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OCCASIONAL PAPERS OF THE MUSEUM OF
ZOOLOGY
UNIVERSITY OF MICHIGAN >
ANN ARBOR, MICHIGAN PUBLISHED BY THE UNIVERSITY
Weed Wine [Ljo2
THE MOLLUSCA COLLECTED BY THE UNIVERSITY
OF/ MICHIGAN WALKER) EXPEDITION, IN
‘SOUTHERN VERA CRUZ, MEXICO. /I
By H. Burrincton BAKER /
ie
INTRODUCTION
The specimens on which this paper is based were collected
by the University of Michigan-Walker Expedition, during six
weeks (July 10 to August 20) in the summer of 1910. The
expedition consisted of Alexander G. Ruthven and his wife,
Florence HP Ret wie para poruCular attention to the
amphibians and reptiles, and the writer, who was primarily
interested in mollusca.
The work of identification and description was made pos-
sible by the Academy of Natural Sciences of Philadelphia,
which generously put at my disposal its extensive collections
and exhaustive library. As a result, any credit that this paper
may deserve is largely due to Dr. H. A. Pilsbry, whose con-
2 University of Michigan
stant advice and assistance is the reason behind its producion.
The writer did the detailed work and the drawing, and an;
‘naccuracies or errors of judgment that may appear can safely
be laid to him. The drawing and photography were done at
the zoological laboratory of the University of Pennsylvania.
‘ _vcauied . uay of the environment of the region has
already been published,’ it is only necessary, in this paper, to
present again the location of the region and to summarize
hrieily the ecological habitats.
LOcATION
All of the collection was made on or within a few miles of
the Hacienda de Cuatotolapam, except one day’s work at the
Laguna de Catemaco, about twenty miles away. The hacienda
(map in Ruthven’s paper; /. c.) lies between the Rio San Juan
and the Arroyo Hueyapam, a tributary, in the Canton of Aca-—
yucan, southern Vera Cruz. This is approximately 18° N.
Latitude and 95° W. Longitude, and about 50 feet above sea-
level. The country is quite typical of the tropical lowlands,
and the collections were made during what is known as the
wet Season.
The Laguna de Catemaco is a few miles to the north in the
heart of the coastal San Andreas Tuxtla range, and not fat
fromthe city Vf Gan Andreas Tixtla_ This lake also drains
into the San Juan River system. ‘The range anu «_ a1,
basin appear to be of volcanic formation. The altitude of the
latter is not definitely known to me, but is probably not more
than 2000 feet above sea-level. From the appearance of this
region, a considerable difference in the molluscan population
1 Ruthven, A. G., 1912. The Amphibians and Reptiles Collected
by the University of Michigan-Walker Expedition in Southern Vera
Cruz, Mexico; Zool. Jahrb., XXXII, abt. f. Syst.; pp. 295-330; pl. vi-x1.
Occasional Papers of the Museum of Zoology 2
would probabiy be found, but the visit was too short to ascer-
tain the fact.
FcoLocy
Here is simply included a brief classification of the habitats,
which is practically that of Ruthven (J.c.), where the details
are presented and illustrated by photographs. A review of
the molluscan inhabitants of the various environments will be.
given in another paper.
A. Terrestrial Habitats.
I. Lowland forests. The dense jungle of the untouched
flood-plains. Two ecological strata are recognized here: (a)
the ground stratum, which includes the leaf-humus, rotting
logs, and other debris; and (b) the arboreal or subarboreal
stratum, under which are taken up the species obtained from
the trees and bushes themselves, both from the leaves and the
trunks.
II. Lowland forest clearings. These may be subdivided into
. three classes: (a) partially cleared places along the Arroyo
Hueyapam (bush and a few clumps of large trees) ; (b) the
burnt-over ground (mainly dead shells obtained); and (c)
cleared fields (the fields of sugar cane and corn and the roads
and guardas rayas between them).
III. Savannah forests and thickets. Clumps of bush and
relict jungle, usually on higher ground, and of a more xero-
phytic type. The yuccas and spiny palms are especially prom-
inent, scattered in clumps through the mesophytic vegetation.
The ground stratum (a), and the subarboreal stratum (b),
may also be recognized here.
IV. Savannah grassland. The grazed, prairie-like portions,
probably due to disturbance by man and cattle. They are
practically without molluscan life.
4 University of Michigan
B. Aquatic Habitats.
V. Lowland forest ponds. Swamps and pools, mainly tem-
porary, in the forest itself and in the cleared regions. ‘The
two main classes studied are: (a) pool-swamps in the low
jungle along La Laja; and (b) the pools in the burnt-over
region and cleared land.
VI. Savannah ponds. Established ponds in the savannahs.
Although the Laguna de Chacalapa is about a mile in length,
it is not over a meter deep at the height of the wet season.
Only one shell was obtained.
VII. Rivers and lakes. a. La Laja. This is what is known
in many Spanish-American countries as a camo (literally, a
sewer). It is a sluggish stream and black-water channel off
of the Arroyo Hueyapam, and does credit to its Spanish —
designation.
b. Sand-bars of the Arroyo Hueyapam. At the hacienda,
the Hueyapam consists of a steep-banked channel about fifty
yards by twenty to thirty feet deep, which, dependent upon
the weather, may contain anything from a sizable creek, with
pools, little rapids and sand-bars, to a raging torrent that com-
pletely fills or overflows it. It is quite typical of the scoured,
sandy creeks so common in the tropics.
c. Rio San Juan. A quite large river, which was in flood at
the time visited, and in some places over-reached its banks for
almost half a mile. Its bottom is probably sandy.
d. Laguna de Catemaco. A deep-basined crater (?) lake,
several miles in diameter. Most of the shore is of volcanic
rock and it contained several rocky islands, but near the out-
let and in some other places this is covered by a deposit of
humus-material. The latter developed, in some parts, a mag-
nificent border of water-hyacinths, a hundred yards wide or
more. Collecting was also done in a small, but very deep, body
Occasional Papers of the Museum of Zoology 5
of water, near the town of Catemaco, and about a hundred
yards from the lake, which fills the crater of a small subsidiary
cone.
ACKNOWLEDGMENTS
I wish to add my thanks to those of Dr. Ruthven, already
' expressed, to all of the Americans at the Haciendas of Cuato-
tolapam and Hueyapam, for their kind hospitality and gener-
ous assistance. In addition, I wish to express the greatest
indebtedness to Dr. Ruthven and wife, for help in every way.
As already mentioned, I owe the very production of the
paper to the generous and patient advice and instruction of
Dr. H. A. Pilsbry. Mr. Vanatta was always a ready addi-
tional help. I also express my indebtedness to Dr. Bryant
Walker, whose generosity made the collection originally pos-
sible, and whose continued advice has been very helpful.
Acknowledgment is also made to the many members of the
staff of the zoological laboratory of the University of Penn-
sylvania, who have been of assistance in the production of
the photographs.
Part I. THe UNIONIDAE OF THE SAN JUAN RIVER SystTEM
Unfortunately, the water was high, so the only living naides
obtained were a few small specimens of A. sapotalensis (1,ea)
and a number of juvenile individuals of a form near A.
umbrosa (Lea) from the Arroyo Hueyapam (H, vii, b).1. In
addition, other shells from the Arroyo Hueyapam and La
Laja (H, vii, a) were picked up on the sand-bars and in the
streams themselves.
Fortunately for the collector, some of the natives of the
region collected the uniones at low water, for the purpose of
1The Roman numerals and letters, throughout the paper, designate
the habitats, as classified in the introduction. In order to distinguish
them from the references to the plates, they are preceded by the letter H.
6 University of Michigan
baking the shells to make the quick-lime used to soften maize
in the preparation of tortillas, the national Mexican bread-
stuff. The shells from the Laguna de Catemaco (H, vii, d)
were obtained, through the intervention of the Spanish gen-
tleman whose hospitality we enjoyed, from a pile (all of one
species) at the edge of the town of Catemaco. They probably
came from the mucky-bottomed portion of the shore, near the
outlet. All of the shells from the Rio San Juan, except the
one specimen of Anodonta, were bought (for one peso) from
a peon at the village of Cuatotolapam, on the hacienda of the
same name. He informed me, through the medium of Mr.
Thomas La Rue, the subgerente of the plantation, that they
were obtained, during low water, from a depth of a few feet
in the Rio San Juan, near the town (H, vii, c).
UNIONIDAE
Amblema (Megalonaias) nickliniana ( Lea) (1834).—One
small left valve, from the Rio San Juan (H, vii, c). Measure-
ments?: length, 86 mm.; height-index at beaks, 75 per cent
(64.5 mm.); height-index at wing, 80 per cent (69 mm.)
diameter-index, 37 per cent (32 mm.).
From the specimens labeled Q. eightsti (Lea) in the A. N.
S. P., that form, which Simpson (1914) regarded as a syno-
nym of Q. heros (Say), resembles some specimens of the latter
species less than it does Q. nicklimana. At least, it looks as
if the range of variation in Q. heros, as used by Simpson, is
1The measurements of the naiades in this paper are given in the
same order and with the same significance as in Simpson (1914), except
that, instead of the height and diameter, the height-index and diameter-
index are given. The index of the height is taken as the height divided
by the length; that of the diameter, the diameter divided by the length.
Both indices are expressed as percentages. Except in the case of quo-
tations, the indices are followed (in parentheses) by the actual dimen-
sions in millimeters. ‘
Occasional Papers of the Museum of Zoology af
much greater than the divergence of Q. nickliniana from some
of its forms.
Elliptio (Leptonatas) ravistellus (Morelet) (1849).—One
dead specimen along Quebrada Laja (H, vii, a). Measure-
ments: length, 48.5 mm.; height-index, 51 per cent (25 mm,) ;
diameter-index, 33 per cent (16 mm.).
The specimen somewhat resembles this species, although a
larger set might show constant differences. In this individ-
ual, the general shape approaches that of E. popeti (Lea); it
is somewhat compressed laterally and has a tendency to be
subsinuate ventrad. The ridges are closer and finer than in
typical Z. ravistella, so that the dry shell has a grayish appear-
ance. When wet, the golden-yellow ground-color, with rather
diffuse, olive-green rays, is apparent. The posterior, dorsal
region is marked by two quite deep furrows, and between
these the surface is wrinkled irregularly, in a manner remotely
suggestive of the Sphenonaias group. The pseudocardinals
are lamellar and very oblique, especially in the right valve.
Unio ravistellus Morelet is the type of the section Leptonaias
Fischer and Crosse (1894), which I use here in the sense of
Nephronaias Frierson (1917). Unfortunately, Simpson (1900)
chose Nephronaias Crosse and Fischer (1894) (type U. plica-
tulus Charp. in Kuster, 1856) as the name of his mixed
assemblage of Elliptio-like and Lampsiline species. Frierson
separates these and retains the name for the unionine shells,
on the supposition that U. plicatulus is such a species. Von
Martens (1900), however, places this species in the synonomy
of A. aztecorum (Philippi). Personally, I think it is rather
A. medellina (Lea). It is true that the surface looks like the
Elliptio-group of Southern Mexico and Central America, but
all of Kuster’s figures look remarkably alike; also the descrip-
tion mentions fine, close-set wrinkles, but these are also present
8 Umiversity of Michigan
in A. medellina, to a certain degree, and a darkening of the
epidermis appears to be a characteristic of many individuals
of all species from the Medellin River. On the other hand,
the block of teeth in the left valve (the individual teeth are
indistinguishable) forms an almost equilateral triangle, and is
set quite far anteriad and ventrad, as in A. medellina, while
in Leptonaias they form an acute-angled triangle with the
smallest angle posteriad, and set up more nearly under the
beaks, as well represented in Lea’s figure of U. persulcatus
(Obs. WEL xien25)9 ulin saddition. athe color ot the mackemis
that of A. medellina and it comes from the same river. How-
ever, the figure also very much resembles some of the more
elongate, smooth forms of &. plexus (Con.), and the dimen-
sions fit either species. For this reason, the best place for
U. plicatulus, and the section Nephronaias with it, is under the
synonomy of A. medellina (Lea), along with U. purpuriatus
(Say), and sharing the same question-mark! Therefore,
Leptonaias Crosse and Fischer (1894), type U. ravistellus
Morelet, is used here as a subgenus of Elliptio, to include those
southern Mexican and Central American forms, with the pecu-
liar ornamentation, included in the genus Nephronaias as used
by Frierson (1917). Coenonaias (type U. aeruginosus Mo.)
and Simononaias (type U. tabascoensis “Charp.” Ktister) are
synonyms. Both owe their origin to Crosse and Fischer (1894).
Elliptio (Sphenonaias) plexus (Conrad) (1838). Plate I,
figs. 4 and 5.
Unio coloratus “Charp.” Kiister (1856).
2 Unio plicatulus “Charp.” Kiister (1856).
Unio pigerrimus (C. and F.) (1893).
Three small specimens from the Rio San Juan (H, vii, c)
closely resemble the smoother forms of this species. They
represent, I believe, a depauperate race of the following form.
Occasional Papers of the Museum of Zoology 9
The hinge-armature is similar to that of juvenile specimens,
and the color of the nacre is that usual in medium-sized indi-
viduals—i. e., lavender with copper tints. However, the shells
are solid, somewhat inflated, and much eroded at the beaks,
and have every external appearance of mature individuals.
One (fig. 5) is quite sinuate on the ventral margin. They
measure :
Length Height-index Diameter-index
Fig. 4 50 mm. 60 (30 mm.) 39 (19.5 mm.)
Fig. 5 54 mm. 61 (33 mm.) 39 (21 mm.)
Another 55.5 mm. 58 (32 mm.) 42 (23 mm.)
E. plexus 55 64 44 (Simpson, 1914)
U. pigerrimus 59 65 46 (C. and F., 1894)
Unio coloratus has every appearance of a smooth specimen
of this species. The question of U. plicatulus has already been
discussed. U. pigerrimus easily falls within the range of varia-
tion of this and the following form.
The section Sphenonaias C. and F. (1894) Pe. U. lieb-
mannt Ph.) is used here to include, besides the type, the more
Elliptio-like forms of Psoronaias (type U. psoricus Morelet).
The typical forms with higher umbones have much more the
appearance of some of the southern species, placed by Simp-
son (1914) in Quadrula, but which were also included in the
section Psoronaias, as originally described. The section Bary-
naias C. and F. (1894) is described in Part VII of the “Moll.
terr. et fluv. de Mex.,” with U. pigerrimus as the single example,
while in Part VIII that species is put under Psoronaias and
U. sallei is listed as the sole example of the former section.
Barynaias is thus a synonym of Psoronaias. Von Martens
(1900) mistakenly calls U. sallei the type of Pachynaias C.
and F. Barynaias is also a synonym of Sphenonaias, as used
IO University of Michigan
here. Sphenonaias should not go into the synonomy of Psoro-
naias, nor vice versa, until the anatomy of a typical example
of either section has been studied; the group whose anatomy
is unknown should be placed, at least temporarily, in the
synonymy of the one studied, so as to reduce the chances of
future confusion. ;
Elliptio (Sphenonaias) plexus, subspecies distinctus (C. and
) (803)). Plate Inthe. 2 - plates splate UNI ite. i 5saiei—
Thirty-nine specimens, including odd valves, from the Rio
San Juan (H, vii, c). This is a very variable form; nothing
about it seems constant. The sculpture varies from almost
perfectly smooth to plicate (typical forms), and finally pus-
tulate. The shape varies from quite close to that of the next
species to a quadrate form which resembles U. testudineus
Morelet. Some of the older specimens have the biangular
posterior margin and the double ridge of U. morini Mo. It
seems probable that Lea was quite right when he combined
E. plexus with E. crocodilarum Mo., as some specimens of this
intermediate form are indistinguishable from the latter shell.
E. plexus crocodilarum (Mo.) may still be retained, as a sub-
species, for the usually larger and more cylindrical, southern
form. From the variation in E£. plexus distinctus, it seems
probable that both U. morimi and U. testudineus are synonyms
of E. plexus crocodilarum, or the second may be a subspecies.
E. semigranosus (von dem Busch), from the Panuco River
system, is a considerably more compressed form, and may be
a separate species, although a series in the A. N. S. P., from
the Tecomate River, are more or less intermediate between it
and the present form. It is, at least, a very distinct northern
subspecies. Unio corium Reeve appears to me to be a distinct
species, more closely related to E. psoricus (Mo.) than to the
present group.
Besides this variation in the larger specimens, this subspecies
(distinctus) varies a great deal with age. The younger shells
are much more compressed in shape and have a whitish nacre,
although they quite early assume the coppery tint. Their
Occastonal Papers of the Museum of Zoology II
hinge armature is quite similar to that of &. liebmanni (i. e.,
the pseudocardinals are more apt to be compressed, quite sim-
ple, and more or less oblique—fig. 15, plate IIT). However,
the laterals are always proportionately shorter and more
curved than in that species, although in this, as in other char-
acters, the two species somewhat approach each other. As is
true of all of these shells from the Rio San Juan, the early
erosion of the beaks and the constant malformation (due to
tropical floods?) cause many small individuals to have every
appearance of an adult shell. For this reason, and because the
specimens in the A. N. S. P. (among them the type) have
the juvenile pseudocardinals of this species, I am inclined to
believe that P. kusxensis Frierson (1917) is a depauperate,
small stream form, closely related to E. plexus crocodilarum
(Mo.). However, the general appearance is certainly that of
completely adult shells.
In all of the specimens of this series of E. plexus distinctus
the beaks are eroded, but the smaller specimens retain enough
to lead me to believe that the beak sculpture of this species
consists of very irregular, but more or less parallel wrinkles,
disturbed by radial plicae and pustules, with a slight tendency
to be doubly looped, rounded on the posterior slope and with
an oblique V on the anterior one, so that the sculpture appears
to run obliquely postero-ventrad.
Plate II, fig. 13, shows a very peculiar, compressed and
slightly sinuate shell, which looks quite like a different species.
The nacre and the general shape of the inside of the shell, as
well as the lateral teeth, are quite typical of distinctus, but the
pseudocardinals are of the juvenile type; that is, they are com-
pressed, almost equal and oblique (figs. 3 and 15 are similar).
The beaks are eroded, but the remainder of the shell shows
no sign of ornamentation, and is almost black, smooth and
shiny, with evident, fine, radiating striations. Other specimens
approach it in various characters, but it combines so many
peculiarities that, if found in lage numbers, it would seem to
require at least distinct racial recognition.
12 University of Michigan
The pseudocardinals of the figure of the type of £. plexus
distinctus (C. and F., 1894) resemble the juvenile form, but
the description sounds more like those of the adult, in which
the posterior pseudocardinal of the right valve is very heavy,
jagged, and almost quadrate.
VARIATION IN EF. plexus distinctus (C. and F.)
E
&
=
as
0
5
Ho
E. semigranosus 98
E. plexus distinctus 79
E. plexus crocodi-
larum 90
U. testudineus Mo. 91
U. morini Mo. 75
P. kuxensis
Frierson 50
Plate I, fig. 3 38.5
Plate II, fig. 8 59.5
fig. 16 62
fig. 15 67
fig. 17 690
fig. 9 69.5
fig. 14 75
fig. 10 77-5
fig. 13 80
fig. II 82.5
fig. 18 82
fig. 12 84
fig. 19 94
Mean of 39
specimens 75.0
ao | Height-index
w
in per cent
ie)
70 (47.5)
72(50.5)
64(48)
69(53.5)
60(48)
67(55)
61 (490.5)
61(51)
61(57)
64
Extremes of lot 38to94 60to 72
Diameter-index
in per cent
32
42
46
37
37
34
33 (12.5)
39(23)
40(25)
42(28)
36(25)
37 (26.5)
35 (26.5)
44(33-5)
35 (28)
51 (42)
43(35)
50(42)
42(30)
4I
33 to 48
(type, C. and F., 1894)
(type, /. c.)
(Simpson, 1914; C. and F.
same proportions, but
smaller specimen)
(C. and F., 1894)
(C. and F., 1894)
(Frierson, 1917)
(Cf. kuxensis)
(distinctus sculpture)
(nearly smooth)
(practically smooth)
(plicate to pustulate)
(Cf. testudineus)
(distinctus sculpture)
(sculptured dorsal)
(peculiar, smooth shell)
(all sculpture eroded)
(compare morini; double
posterior ridge)
(Cf. crocodilarum; heavy)
(largest spezimen)
Occasional Papers of the Musewm of Zoology 13
Elliptio (Sphenonaias) liebmanni (Philippi) (1847),
subspecies cuatotolapamensis, new subspecies
Plate I, figs. 6, 7; plate III, fig. 22 (type) ; plate IV, figs. 20-25.
Twenty specimens; including odd valves; from Rio San
Javan: CEL vate).
Shell of medium size, elongate subelliptical to subrhomboid,
quite solid, convex, with posterior ridge well marked, sub-
angular or often rounded and sometimes double; beaks weli
anterior, sculpture (as interpreted from remains of smallest
specimen) probably somewhat similar to that of FE. plexus,
only not so oblique, and broken by the radial plications so as
to give it an almost radial appearance (at least suggestive of
some of the South American genera); anterior end evenly
rounded or subangular just in front of lunule; posterior mar-
gin gradually curved, sometimes quite markedly biangulate
behind; basal line very slightly rounded to subsinuate, post-
basal point but little elevated; epidermis (in older shells) dark
brown to almost black, roughened to smooth and shiny, with
fine, radiating striations (in younger shells with golden-yellow
ground-color, almost completely obscured by diffuse olive-green
rays); surface of shell usually marked by vertical furrows
(which start high on the beaks and more or less disturb the
beak sculpture), most prominent on and just behind the ante-
rior slope, usually not extending more than 30 mm. ventrad
from the beaks, and rarely by radiating, dorsally curved plica-
tions as in &. plexus; left valve with two pseudocardinals, the
anterior compressed, almost lamellar and very oblique, the
posterior trigonal or compressed ventrally so as to be wedge-
shaped, and two, elongate, almost straight laterals, of which
the more ventral is better developed; right valve (II, 22) usu-
ally with two, subequal, compressed, almost lamellar, and very
oblique pseudocardinals, although sometimes the anterior is
14 University of Michigan
partially suppressed and in old shells both become jagged, and
usually one well-developed, slightly curved, long lateral, with
sometimes an indication of another more dorsad; beak cavi-
ties rather shallow, showing or just obscuring the dorsal scars ;
anterior muscle scars deep and sculptured by anastamosing
lamellae; posterior scars well impressed only at the anterior
end; nacre white to salmon or lavender, without distinct, cop-
pery tinge; radially striate and iridescent in the younger shells,
but thickened and minutely pebbled anteriad in the older
specimens.
VARIATION IN &. liebmanni cuatotolapamensis, n. subsp.
So Rs
an ace:
SO eG » a
cy ey oO a,
ae) 5
z v= 8.8
pe ey a
E. liebmanni 103-56 43 (Philippi, 1849)
E. sphenorhynchus 71 52 33 (C. and F., 1894)
Fig. 6 (smallest) 55 51(28) 33(18) (heavily ornamented )
Fig. 7 (left valve) 62 50(31) 34(21) (ornamented)
Fig. 20 (right valve) 62 58(36) 37(23) (see below)
Fig. 21 65 55(30) 34(22) (smooth and shiny )
Fig. 24 74 54(40) 33(24) (ornamented)
Fig. 23 (left valve) 78.5 48(38) 29(23) (smooth; see below)
Fig. 25 (very heavy) 79 53(42) 42(33) (strongly eroded)
Fig. 22 (type sub-
species) 81 53(43) 35(28) (ornamented)
Meanof2ospecimens 69 54 34
Extremes of lot 55-83 48-58 29-42
This is a smaller form than typical liebmanni, with, appar-
ently, a stronger tendency towards ornamentation. Simpson
(1914) omits any mention of the ornamentation in his descrip-
tion of E. liebmanni, but Philippi (1849) says: “The beaks
of my examples are very widely and strongly eroded; how-
Occasional Papers of the Museum of Zoology 15
ever, on one I still recognize vertical, shallow furrows, which
are about a line apart and extend almost an inch from the
beaks, which must give an individual character to the young,
uninjured shell, that helps to differentiate this species from
others” (translation). The locality of the species is indefinite
(Mexico, legit cl. Liebmann), but it is probably a more south-
ern form than this subspecies. U. sphenorhynchus C. and F.
(1894) has the same dimensions as the subspecies, but is very -
sinuate ventrad; has a much more definitely marked posterior
ridge; the beaks are placed more posteriad; and the posterior
tooth in the right valve is more trigonal than compressed. C.
and I. (1894) also give a figure (lxv, 4) of what they con-
sider an aberrant shell of their U. tehuantepecensis; it has
every appearance of my shell, plications and all.
This species is apparently quite closely related to E. plexus
(Con.) and its identification is further confused by the very
great resemblance to what I think to be the young shells of
A. walkeri (see below). These latter are intermediate in shape
between &. plerus and &. liebmanni, and their lateral teeth
somewhat resemble those of the former. However, their right
pseudocardinals are more trigonal and they lack the vertical
furrows, typical of both species, although they possess some-
what similar, curved, posterior plications.
Two quite well-marked lines of variation are present in the
lot. One is represented by figs. 20 and 21, and by two other
shells not figured. These four shells are much smoother and
more polished than are the rest (21 has no sign of ornamen-
tation), have a more strongly curved, dorsal line, and shorter
and more curved laterals, and tend to be somewhat higher.
The last two of these characters make them approach, in
appearance, the young shells of 4. walkeri and E. plexus. The
other aberrant type is represented by a single left valve (fig.
16 University of Michigan
23). It is a considerably more elongated and compressed form
than are the others, and the epidermis is golden-brown with
indistinct, brownish rays. The growth-lines are well marked
and give this shell a somewhat concentricly wrinkled appear-
ance; otherwise it appears quite without ornamentation.
Anodonta globosa Lea, subsp. nopalatensis (Sowerby)
(1867).—Plate V, fig. 26. One left valve, in good condition,
from the Rio San Juan (H, vu, c) ; picked up on the bank by
' Dr. Ruthven.
The epidermis is radially striate, % mm. apart, while ante-
rior to the umbones are etched very distinct, fine furrows, 4
to 6 mm. apart. The ventral margin is distinctly sinuate, but
this may in part be caused by an injury about 3 cm. dorsad;
but the shell is flattened to slightly concave centrally, even
above this. The color of the epidermis is dark brownish-olive,
to rust-colored towards the beaks.
This specimen is from within a few miles of the type locality
of nopalatensis, as worked out by von Martens (1900); A.
globosa globosa is froma lake near the mouth of the same river
system. With its extremely high and full beaks, great infla-
tion and sloping dorsal margins, this form appears to be more
distinct from globosa (adult specimens in the A. N. S. P.)
than is A. tabascensis Mo. as figured by Fischer and Crosse
(1894).
MEASUREMENTS
A
oR Bl. ele
Se ae
Snes o =I
= » oO ~~ oO
~ SG vo a,
o 0 4 e o
cco) (by SG =} mas) oS
a la
A. globosa Wea. 100 72 52 (type, Simpson, 1914)
A. tabascensis Mo. 178 69 50 (F. and C., 1894)
A. nopalatensis
Swby. 150: (73 (F. and C., 1894)
Plate V, fig. 26 150 75(112.5) 68(102)
Occasional Papers of the Museum of Zoology 17
Actinonaias sapotalensis (Lea) (1841), and approaching
subspecies computata (Crosse and Fischer) (1893).—Seven
specimens from Arroyo Hueyapam (H, vii, b); 8 from Rio
San Juan (H, vii, c). The former include the specimens of
which the anatomy has been described and figured by Ortmann
(1912).
The specimens from the Arroyo Hueyapam are near sapo-
talensis, while those from the Rio San Juan approach compu-
tata, which, from the proportions and the figure of the hinge
armature, appears to be the description of a youngish indi-
vidual of a considerably larger form, from the Goatzalcoalcos
River system. One of the larger specimens is arcuate ventrad
very much like some of the specimens of P. opacata (plate
VII). In these older individuals, the wavy tendency of the
rays becomes accentuated towards the ventral margin, until
they are broken into very pronounced zig-zags, similar to some
of the species of Plagiola.
MEASUREMENTS
5
= Raney Sel the
& YG S| @
Goi aoe
a ag ey 2S
op op s
Satie. SS
or ee an)
A, sapotalensis 56 64 41 - (Simpson, 1914)
A. s. computata 77 68 39 «6. (C. and F-,, 1894)
Arroyo Hueyapam 50.5 62 34 (young male)
53.5 65 39. «© (female)
Rio San Juan 70.3 67 44
7950 O50 44
(largest) 8 65 49 (arcuate ventrad)
Extremes 50-81 58-67 33-49
Actinonaias umbrosa (Lea) (1856) and approaching expli-
cata (“Mo.” C. and F.) (1894). :
U. alienigenus C. and F. (1893). Plate VII, figs. 43-47.
Five adult shells and 15 juveniles from the Arroyo Hueya-
pam (H, vii, b) ; 12 specimens, including odd valves, from Rio
San Juan (H, vii, c).
18 University of Michigan
The small river form (Arroyo Hueyapam) approaches quite
closely A. wmbrosa (Lea), as it has the more wedge-shaped
form (figs. 44, 45), but the specimens are quite light-colored,
while most of those from the Rio Medellin, like so many spe-
cies from that river, are quite dark. Some of the adult
males(?) from the Rio San Juan (fig. 46), on the other hand,
quite closely approximate U. alienigenus C. and F. or even
A. explicata. The females(?) from the Rio San Juan (fig.
47) are not so rectangular as the males and are somewhat
swollen along the posterior shoulder down to the posterior
ventral margin, very much as in A. sapotalensis, although to
a lesser degree. The young males of the last species are prac-
tically identical in shape with those of this form, but may be
easily separated by the difference in the pseudocardinals. The
juvenile specimens from the Arroyo Hueyapam (fig. 43) are
subrhomboid, and are beautifully rayed with green. ‘They
have no sign of a dorsal “wing.” The pseudocardinals of the
right valve are always oblique and almost parallel, but the size
of the upper tooth is variable and the development of either
appears dependent on the age of the individual. In the juve-
nile specimens, they are lamellar, while in the older specimens,
although always distinctly compressed, they are often quite
heavy and jagged. The nacre of the adults is usually white,
but may be tinged with either salmon or violet.
Although typical specimens of 4. wmbrosa and A. explicata
are very dissimilar, these two lots of shells show approaches
to both species, and it seems probable that wmbrosa is a
dwarfed, small-river, northern form (type apparently a female)
of the same species of which explicata is the larger, southern,
form (type apparently a male). U. alienigenus is an interme-
diate form from the Goatzcoalcos River system. Strictly
speaking, A. umbrosa (Lea) should have the priority, as More-
Occasional Papers of the Museum of Zoology 19
let’s description, like so many in the Test. Nov. (1849), was
totally unrecognizable until 1894, when it was beautifully fig-
ured, from original specimens, by Fischer and Crosse. How-
ever, as the general tendency in North American uniones seems
to be to accept types regardless of the recognizability of the
descriptions, A. umbrosa will perhaps ultimately become a sub-
species of A. explicata, as the original naming of the latter
(1849) has the priority.
Mesonaias C. and F. (1894) (type U. explicatus Mo.) is
used here as a synonym of Actionaias. Graphonaias, of the
same paper, has already been placed in the synonymy of the
latter by Frierson (1917), who lists the type species (U. medel-
linus Lea) as an example of that genus.
From the original comparison, L. sapperi von Ihering (1901)
appears to resemble an old specimen of dA. explicata, with
heavier pseudocardinals and obliquely truncate anterior end,
but the dimensions are those of a more elongate and compressed
form. The original notes of comparison, without figure, are
too brief to assure its determination.
MEASUREMENTS
3
S S oy
Be oo So
5 OS So
ame Q
A. explicata TOME 57) 33 (F. and C., 1894)
U.alienigenus 82 62 37 (F. and C., 1894)
A. umbrosa 90 6=— 5g 33 (Simpson, 1914)
L,. sapperi 114 49 20 (von Ihering, 1901)
Arroyo Hueyapam:
Fig. 43 21.5 56(12) 32(7) (smallest juvenile)
Fig. 44 Aue Or (25) 375)
Fig. 45 71 62(44) 36(25.5) (compare umbrosa)
Rio San Juan:
Fig. 46 94 63(50) 35(33) (male? compare explicata)
Fig. 47 93-5 62(57.5) 40(37) (female?)
20 University of Michigan
Actinonaias (Disconaias) walkeri, new species
Plate I, figs. 1 and 2; plate IX, fig. 49, type; plate X, figs. 48-50;
plate XI, figs. 48 and 49
Fifteen specimens, including odd valves, from Rio San Juan
CE vite):
Shell rather large; male(?) subrhomboid, elongate, com-
pressed, often slightly sinuate below; female(?) subelliptical,
rather swollen; anterior end rounded, with dorsal margin con-
siderably lower than beaks and the ventral margin obliquely
truncate; posterior end with dorsal margin equal (males?) or
higher (females?) than the beaks; posterior ridge double,
rounded to subangular in the males(?), while the region is con-
siderably swollen in females(?); posterior margin moderately
biangulate; beaks rather low, behind the middle, and curved
posteriad, especially in the females(?); sculpture (if identi-
fication of juvenile specimens is correct) probably consisting
of fine, concentric wrinkles, flattened ventrad ; epidermis rough-
ened by irregular growth-lines which are sometimes markedly
sulcate, especially near the ends of the shell, radially striate
throughout and sometimes with dorsally curved sulcations on
the anterior slope; color brownish with very indistinct olive-
green rays in adult (rays diffuse on a yellowish background
in juvenile shells) ; left valve with two stout, trigonal, jagged
pseudocardinals, and two heavy, short laterals (fig. 49, plate
XI) ; right valve with two pseudocardinals, the anterior small -
to vestigial, oblique; the posterior large, stout, trigonal, almost
vertical, and broken superficially by vertical, jagged lamella-
tions; with cavity for reception of posterior left pseudocardi-
nal, usually deep and large; followed by a small tooth; and
with one very heavy, club-shaped, short lateral; hinge-plate
heavy, short, occupying middle half of dorsal margin, curved
below in male(?) and almost arcuate in female(?); beak cavi- .
Occasional Papers of the Museum of Zoology 21
ties rather shallow, just obscuring dorsal scars ; anterior muscle
scars deeply impressed but quite smooth; posterior scars
well marked but not impressed ; pallial line deep, crenate ; nacre
white to reddish violet, almost scarlet, sometimes with a cop-
pery tinge, thickened anteriad, iridescent posteriad; edge of
inside of shell, due to obliquity of prismatic layer, with white
to rust-colored border 2 to 4 mm. wide.
Mi&ASUREMENTS
4 Y ino} pea
Ss 2S re o te
a 2G De
Seoest ee
ye A
A. disca (Lea) 13256103 27 (type, Lea, 1838)
135 Gy/ 24 (Simpson, 1914)
A. disca fimbriata(Fr.) 80 59 31 (Frierson, 1907)
Fig. 1 46 52(24) 30(14)
Fig. 2 6r 56(34) 34(21)
Fig. 48 (right valve) 97 65(63) 41(40) (female?)
Fig. 49 105 57(60) 34(36) (type; male?)
Fig. 50 (left valve) TO25 571050) oi (32) Gnale®)
Extremes (11
adults) 88.5-100.5 55-05 31-45
The larger shells of this species seem to be markedly dimor-
phic; those that appear to be the old males somewhat resemble
L. fimbriata Frierson (1907), while those taken for old females
have the slightly hooked beaks and the humped posterior dorsal
margin of U. discus Lea (1838). On account of this dimor-
phism and the resemblance of the two sexes (?) to these two
forms, I think it is probable that Unio discus (more normal
development U. panacoensis von d. Busch) is largely based on
old female specimens which have reached, in the quieter water
of the large river near Tampico, their completely distinctive
form, while L. fimbriata Frierson, also from the Panuco River
22 University of Michigan
system, is a small-stream form of the same thing, mainly
described from males and from rather immature females that
had not yet developed the characteristic shape of the older
specimens. The epidermis, hinge armature, obliquity of the
prismatic layer and nacre of the two forms are practically
identical, except that typical L. fimbriata plainly shows its
exposure to a more severe environment. A youngish shell,
approaching L.fimbriata, in the A. N. S. P. from “near Tam-
pico,” perhaps represents the male of typical A. disca (Lea).
Some of the young shells of disca in the A. N. S. P. are indis-
tinguishable from some specimens of L. fimbriata, which might
be regarded as females that had not yet completely developed
the adult dimorphism. )
Ortmann (1912) has already shown that the marsupial char-
acters of fimbriata are those of the general Plagiola-Paraptera-
Actinonaias type. If the hypothesis in regard to the sexual
dimorphism of A. discus is correct, the section Disconaias C.
and F. (1894) (type U. discus Lea) is more or less interme-
diate in shell-characters between Actinonaias and Plagiola, as
the males are more or less Lampsilis-like in shape, while the
completely developed females bear considerable resemblance to
typical Plagiola. The dimorphism of A. disca (Lea) is more
marked than that of A. walkeri, as the females of the latter
species do not differ so much in general shape from the males,
but the shape of the post-dorsal swelling and beaks in the
females is peculiar, and agrees with that of A. disca.
The section Disconaias thus contains two species, one of ©
which may be divided into two subspecies: A. disca disca
(Lea), A disca fimbriata (Frierson), both from the Panuco
River system, and A. walkeri from the Rio San Juan. The
dimensions given in the partial description of L. sapperi von
Thering (1901) are similar to those of A. walkeri, and some
Occasional Papers of the Museum of Zoology 22
of the points mentioned in the original comparison might be
applied to the latter, but I cannot believe that Simpson (1900)
would ever confuse a species, even a male specimen, of this
group with A. explicata.
A. walkeri is smaller than typical disca and, in proportion
to size, is also heavier than either disca or fimbriata. The
females are more inflated than in either of the nerthern forms,
and are usually more elongate. The laterals of A. walkeri are
heavier and lower, in proportion to the size of the shell, and
the main pseudocardinal of the right valve is more broadly
trigonal, with no tendency to be compressed. This last differ-
ence is most notable in the young specimens, as the juvenile
pseudocardinals of A. disca are both quite oblique and almost
lamellar, while those of walker: are quite similar to those of
the adult in shape. The epidermis of walkeri is also thicker,
and the nacre attains a much more pronounced color (although
similar in shade) than in any specimens of A. disca that I have
seen.
Actinonaias (Leptodea?) tecomatensis (Lea) (1841).—
Fourteen specimens, including odd valves, from the Rio San
Juan (H, vii, c). These specimens agree quite well with
typical tecomatensis. This species is very close to the more
northern A. tampicoensis (Lea) (1838).
MEASUREMENTS
é
Sey net
S es AS
ete Rome ae
= is] EG 2 @
oo én &
Sy Sh) et I
mt fa)
A. tampicoensis 80 75 35 (Simpson, 1914)
A. tecomatensis 90 = s«67 44 (Simpson, 1914)
Mean, from Rio San Juan 88 70 45
Extremes, ditto 66:5-96 66-76 40-49
24 University of Michigan
The group of Mexican forms with a tendency towards the
production of dorsal alae, which includes these species, may
be given any one of three names, all sections of Fischer and
Crosse (1894): Cyrtonaias (type U. berlandieri Lea), Del-
phinonaias (type U. delphinulus Morelet), and Phyllonaias
(type U. paludosus Morelet). None of these are used and
they are all included as synonyms of Actinonaias for the fol-
lowing reasons:
I. From the shell characters, they all appear to be more or
less closely related to Actinonaias, although very probably sub-
generically or generically distinct.
2. Until definitely placed in the synonomy of Actinonaias,
anyone who desired a little more variety in the nomenclature
of the North American uniones might possibly have placed
that genus in the synonymy of any of them.
3. The choice of name should be left until the anatomy of
one of the types is thoroughly known. They are all prior te
Paraptera Ortmann (1911).
Plagiola (Artonaias) opacata (Crosse and Fischer) (1893).
—Plate VI, fig. 35; plate VII, figs. 27-38. Fifty-eight speci-
mens from Lake Catemaco (H, vii, d), about one-half mile
from the outlet in the Rio San Juan River system. Although
no soft parts were obtained, the marked dimorphism of this
lot of specimens presents convincing evidence that the type of
U. opacata C. and F. is a female of a species closely related to
Plagiola (Artonaias) saller (C. and F.) (1893).
Checkerboard graphs, showing the variation in length and
the height-index, the variation in length and diameter-index,
and the variation in the two indices, were made for all 58
specimens, and gave bimodal arrangements in each case. Of
the photographs presented (plate VII), the left hand column
and the two central figures are plainly of the female type (figs.
Occasional Papers of the Museum of Zoology 25
27-30, 32, and 33), while those in the right hand column and
the middle figure in the upper row (figs. 31, 35-38) are evi-
dently of the male type. However, young shells are more or
less inseparable and in old age the proportions again often
become similar, as, for instance, the middle figure in the bot-
tom row (fig. 34) looks like a female, but the earlier growth-
lines give more the contour of a male.
The older specimens are practically black and all are dis-
colored, but an application of oxalic acid to some of the
younger ones reveals a beautiful, silky-brown epidermis, often
with quite evident, olive-green rays. The beaks of all are
eroded, but, in two or three of the more nearly perfect speci-
mens, remains were observed that apparently indicate the beak
sculpture to consist of low, rounded wrinkles, with a slight
tendency to be doubly looped. The silky appearance is caused
by the close and regular arrangement of the growth-lines,
which are crossed at right angles (in many specimens) by fine,
radiating striations. At the posterior end, the latter become
coarser and more distinct and are often separated by quite
pronounced ridgelets. This structure appears to be a charac-
teristic of the surface of the shell-substance, and may or may
not affect the epidermis. In some of the older shells, the epi-
dermis has a similar, flaky appearance to that characteristic
of the group Artonaias. As shown by the figures and meas-
urements, the shell is extremely variable and the older, arcurate
specimens bear little resemblance to the younger shells. They
are all connected by intermediates, but the specimens figured
are chosen for divergence rather than resemblance. Fig. 32
shows an especially aberrant form, with much higher beaks,
which are very swollen. The right pseudocardinals are usu-
ally quite equal and compressed (as remarked by F. and C.),
but often the upper is smaller (as pointed out by Simpson,
26 University of Michigan
1914). As the type figure is that of a female specimen, a male
specimen is here figured in some detail (plate VI).
U. mexicanus Philippi (1847) apparently has been confused
with this species by various authors. Crosse and Fischer began
the trouble by placing the two in the same section, without
comparison. Von Martens (1900) remarks that U. opacatus
is “perhaps only a shorter variety of U. mexicanus.’ Simpson
(1914) apparently considered U. mexicanus as practically
unidentifiable, but had a shell like a young opacatus that he
thought satisfied the description of the former. A careful
examination of Philippi’s somewhat blurred, but rather good
figure (1849) (Kuster’s copy as usual is abominable), and a
comparison of the description and proportions, will, I believe,
convince the most skeptical that U. mexicanus is exactly what
Philippi (one of the keenest observers of his time) intimated
that it was: a rather distinct form related to 4. aztecorum
(Ph.)! He wrote, “The epidermis, the nacre, the figure agrees
pretty well with U. agtecorum and at first I held this form
(Art) for a variety of the same, yet there occur the following
differences. . . .” (translation). A specimen in the Wheatley
collection (A. N. S. P.), labeled azgtecorum, approximates
Philippi’s description of- U. mexicanus. The form certainly
has nothing in common with P. opacata except a rather straight
dorsal line.
MEASUREMENTS
4“
a cB)
= Ae SS
eS os 38
S =I ce
= Kal Cy) Oy
fo +» Oo 4 oO
y cs eG Oe
Dey oe
5 Oo oS oS
a ae ja
P. opacata Reh Oy 52 (C.and F., 1894)
A. mexicana 64 58 38 (Philippi, 1849)
Means (male type) BB OM 44
Means (female type) 50.)—Cts«#S5 47
Extremes (58
specimens) 43-66.5 58-75 40-54
Occasional Papers of the Museum of Zoology 27
Plagiola (Artonaias) opacata (C. and F.), subspecies new
?—One specimen from the Rio San Juan quite closely
approximates P. opacata, but has only one right pseudocardinal
(the posterior). With it probably belong two or three much
larger valves, all badly eroded and broken, but which show
a considerably heavier and more arched hinge plate. These
shells perhaps represent large subspecies (river form), but the
material is too scanty and poor to justify a description. In
many ways this form somewhat resembles P. sallei (C. and F.)
(which would have the priority over opacata), but the latter
appears to have higher and fuller beaks (fig. 32, plate VII, is
comparable in this regard), and a trigonal, right posterior
pseudocardinal. Simpson (1914) also speaks of the absence
of radial striations, but they are difficult to find, or are com-
pletely lacking, in the epidermis of some specimens of P. opa-
cata. These large specimens also resemble, to a certain degree,
some of the older shells of A. sapotalensis (Lea), but the latter
may be quite easily separated by their vertical right pseudo-
cardinals, which are trigonal in shape, and by the zig-zag rays.
Lampsilis rovirosai Pilsbry sanjuanensis, new subspecies
Plate VII, figs. 39-42
Fourteen specimens, including odd valves, from the Rio San
Jam. Cal, satiie)).
Shell rather large, subrhomboid to obovate; rather elongate,
subinflated ; posterior ridge well rounded and with two radiate
sulcations on postero-dorsal slope; hinge-line rather short and
quite straight ; beaks rather full and well developed (especially
as compared to A. explicata) ; beak sculpture (from remains
in two younger specimens) apparently consisting of five or
six, rather coarse wrinkles, scarcely looped; epidermis radially
striate, olive-green in younger specimens, shading to yellowish
at beaks and at the edge of the shell, blackish in old specimens ;
growth-lines fine and regular, giving the shell a soft, dull finish ;
left valve with two almost horizontal pseudocardinals, lamel-
late to heavy and jagged, but always compressed, and with two
28 University of Michigan
laterals, the ventral being especially high and lamellate; right
valve with two, parallel, oblique, usually lamellate pseudo-
cardinals, although the upper is vestigial or sometimes almost
completely lacking, while the lower in old shells tends to become
almost trigonal; and with one thin lateral; beak cavities mod-
erately deep, capacious, obscuring the dorsal pits anteriad;
anterior muscle scars well marked, smoothish, separated ; pos-
terior scars larger, confluent, not impressed, concentrically
striate and iridescent; pallial line well marked throughout its
length; nacre white, or tinted with lavender or salmon, some-
what thickened anteriad and delicately iridescent throughout.
The male(?) shell (plate VIII, figs. 39 and 40, type) is sub-
rhomboid, with the posterior ridge better marked and ending
in a rounded point about one-half way up on the posterior
margin. The female(?) shell is more elongate, subovate, and
strongly inflated in the posterior half of the shell, with the
very much rounded posterior point one-half or more of the
height above the ventral margin (plate VIII, figs. 41 and 42).
This subspecies is apparently a smaller form of the more
southern typical rovirosa. The adult female(?) shell also
differs from the type specimen, by a tendency to be somewhat
more strongly inflated and elongate.
Simpson (1900) first pointed out that U. testndineus Reeve
differed from true explicatus Morelet, and named the form
L. lividus. Although I must confess that I am unable to place
some individuals to my complete satisfaction, I think that the
two shells, as Simpson intimated, are not even very closely
related. But, from the material on which the subspecies 1s
based, U. testudineus or L. lividus appears to represent a rather
unpronounced female type, while rovirosai (type in A. N. 8.
P.) is what I believe to be the completely developed, old female,
which has a type of marsupial(?) swelling quite distinct from
Occasional Papers of the Museum of Zoology 29
that of A. explicata (Mo.). If this arrangement is correct,
L. vovirosai Pilsbry shows a much more marked sexual dimor-
phism than does the latter species, where the female is nearly
the same shape as the male but is slightly more inflated along
the posterior ridge and down to the ventral margin. This more
marked dimorphism and the indications of the beak sculpture
(even the younger specimens are somewhat eroded) are the
reasons for the retention of rovirosai in Lampsilis, until the
soft parts are known.
MEASUREMENTS
3
& = ~
Bes oy oe 5
BB Be
2 28 38
eal sl
oO mt
jee a
LL. rovirosat mig Oy 40 (Pilsbry, 1900)
L, lividus 110 =: 50 (Simpson, 1914)
Lr. sanjuanensis
Fig. 39 70.5 61(43) 36(25) (male?)
Fig. 40 82 65(53) 41(34) (type; male?)
Fig. 41 co. 6.: 64(58) _ 4440) (female?)
Fig. 42 98 61(60) 43(42) (female?)
Extremes (14
specimenis ) 64-908 58-65 36-48
Lampsilis ruthveni, new species
Plate XI, fig. 53; plate XII, fig. 53; plate XIII, figs. 51-54
Seven specimens, including odd valves (2), from the Rio
Sam Jcem (isl, with, ©).
Shell rather small, elliptic to subovate, rather solid, inflated
behind middle; beaks in front of middle low; beak-sculpture
not observed ; posterior ridge rounded or shouldered ; posterior
margin with rounded point at or a little below middle of height ;
epidermis smoothish, thrown into sulcations and low, rounded
ridges at growth-lines, dull, golden-brown to dark brown, the
30 University of Michigan
lighter shells with distinct, wavy, greenish-black rays, limited
to the posterior half ventrad but painting the entire length of
the earlier growth; left valve with two pseudocardinals, the
anterior almost vertical, narrow and high, with the anterior
surface forming an almost equilateral triangle and overhanging
the anterior muscle-scar ; the posterior rather heavy, pyramidal
and trigonal; and with two short laterals; right valve with
two pseudocardinals, the anterior small or vestigial and tri-
gonal, the posterior heavy and trigonal; with a deep cavity for
the reception of the posterior tooth of the left valve, often
followed by a low, rounded accessory tooth, and with one short,
stout lateral; hinge plate moderately heavy, usually well
arched, and, in these specimens, extensively invaded by a ven-
tral proliferation of the ligamental material; beak cavities shal-
low, exposing or just obscuring the irregular row of deep
muscle pits at their anterior ends; anterior muscle scars deep,
separate, the largest almost conical with the point of the cone
undermining the pseudocardinals, especially in the left valve,
little but coarsely sculptured ; posterior scars semiconfluent, the
largest spatulate in shape, slightly impressed anteriad, concen-
trically striate and iridescent throughout; nacre white or
tinged with buff dorsad, thickened anteriad, iridescent poste-
riad; pallial line well marked, crenulate.
The male(?) shell is moderately inflated, subelliptical, with
the well-rounded posterior point at about the middle of the
height (plate XIII, fig. 52). The female(?) shell (fig. 51 is
the type) is narrowly or broadly (fig. 53) ovate, much inflated
just posterior to the center, and with two quite well-marked,
but rounded, radiating swellings posteriad: one extending ven-
trad into the posterior point of the shell which is below the
middle of the height, the other reaching the ventral margin
about one-third of the length from the posterior end. ‘The
ventral margin of the female(?) shell is almost straight to
quite noticeably sinuate just in front of the ventral end of the
anterior swelling, and the margin is also often indented between
Occasional Papers of the Museum of Zoology Bi
the projections formed by the ventral ends of the two swell-
ings. Two older shells have a slight arcuate tendency at the
prolonged posterior point, which gives them a peculiar, beaked
appearance (fig. 54). In both of these last, the beaks are
eroded to such a degree that the pseudocardinals show dorsally
as a sinuation of the hinge-line.
This swollen shell is more markedly Lampsilis-like in gen-
eral appearance than are any of the other southern Mexican
naiades ; in fact, if without definite locality, it would undoubt-
edly be taken for a shell from the central United States. The
marsupial(?) swellings even give it a certain resemblance to
the genus Truncilla. All of the specimens are heavily eroded,
as if the shell-substance was softer than usual, which may be
the reason for the ligamental invasion of the hinge plate.
Among the Rio San Juan uniones, Lampsilis ruthveni is
nearest Lampsilis rovirosai sanjuanensis in shape, although
much smaller and heavier, while its color and rays give it a
superficial resemblance to A. sapotalensis. ‘The radiate poste-
rior swellings and the general inflation, especially of the
females(?) are very distinctive characters in a Mexican form.
MEASUREMENTS
~
wm a
BS cae
ws om
S u
ort Os
yy Vv <= @)
6 & oe
Op &
“— o S)
O en Sg a)
an (an)
66(35) 48(25)
Or U1 U1 On a
© AnwW {Length in mm.
On
Fig. 52 64(35) 47(26) (male?)
66(37) 48(27)
Fig. 51 65 (38) 58(34) (type, female?)
Fig. 53 60
72 (43) 52(31) (much higher; female?)
Fig. 54 73 62(45) 46(33.5)
73.5 62(45.5) 46(34)
Means (7
specimens ) 61.5 65 49
Extremes 53-73.5 62-72 46-58
eee Ee eee ea eae
32 University of Michigan
Part II. OPprERCULATES
HELICINIDAE!
Oligyra (Succincta) flavida strebeli (Pfeiffer).
H, flavida Menke (1829). The usually larger, more southern,
banded form.
H. trossula Morelet (1849). A synonym of the preceding.
H. brevilabris Pfeiffer (1857). From description, a still larger
form.
Hi. strebeli Pfeiffer (1861). Usually smaller, thinner and more
depressed, with 5 to 544 whorls; used here as subspecies.
About 800 adults; from leaves of trees, shrubs and vines
(H, I, b), and on the ground (H, I, a) in the lowland forest;
dead shells from the burnt-over area (H, II, a) ; from leaves
of shrubs, cacti, etc., in the savannah forests (H, III, m) ; and
from shrubs and elephant-ears along Arroyo Hueyapam (H,
JEL, 10).
None of the specimens are banded, but the ground-color
varies from vitreous white and milky white, through horn-
colored and greenish horn-colored, to yellow and dark amber-
brown. The last two color-forms are especially striking. The
lip is always milky white. Extremes measure:
Altitude Greatest diameter Heightaperture Diameter aperture
6.1 mm. 93 (5.7 mm.) 48 (2.9 mm.) 52 (3.2 mim.)
4.5 mm. 102 (4.6 mm.) 53 (2.4 mm.) 58 (2.6 mm.) 2
The spiral striations in these specimens are very variable;
they may be quite well developed or almost completely absent.
1The radulae of the four species included here have been exam-
ined and are figured in another paper, “Notes on the Radula of the
Helicinidae,” which will appear in the Proc. Acad. Nat. Sci. of Phil-
adelphia. As the synonymy of the North American mainland species
is also treated in that paper, it is omitted here, except where it is
actually discussed.
2 Throughout this paper, the altitude is expressed in millimeters,
but the other dimensions are expressed as indices. The index of each
dimension is taken as that dimension divided by the altitude. ‘The
index is followed by the actual dimension in millimeters.
Occasional Papers of the Museum of Zoology 33
One specimen from the savannah forests (H, III, b) has a
well-marked indentation on the basal lip of the aperture, and
many specimens show an indication of the same tendency.
These specimens quite closely resemble O. fragilis (Morelet),
which Wagner (1907) places in his subgenus Leialcadia (or
Leicaladia?) of the genus Alcadia.
FHelicina (Tristraiua) zephyrina Duclos (1833).—One hun-
dred one adults, mainly from leaves of trees and shrubs (up
to about 15 feet above ground) in the lowland jungle (H, I,
b) ; also found on shrubs, trees and elephant-ears in the par-
tially cleared region along Arroyo Hueyapam (H, II, a), and
on the leaves of shrubs and on cacti and yucca in the patches
of brush on the savannahs (H, III, b). Shells (mainly dead)
were also found on the ground (where they apparently aesti-
vate) in these places (H, I, a; H, III, a) and also in the burnt-
over meson (Jel, IDL, 1D).
This species aestivates with the operculum almost entirely
closed, but leaves a little crack between its lower edge and the
basal margin of the aperture (fig. 1). Many specimens have
a slight depression on this portion of the aperture margin, with
an adjacent callus or tooth at the base of the columella. This
makes them look very much like the figures of H. deppeana
von Martens (1863). As this series of specimens also
approaches that species in sculpture (as figured), I am rather
inclined to believe that the latter is little more than a subspecies
of the present species. Apparently this condition of the aper-
ture is quite common throughout the family, although best
developed in Alcadia. ‘The operculum of H. zephyrina has
the horny, inner layer well developed and almost scarlet in
color. The calcareous plate is very thin and is usually incom-
plete towards the parietal wall of the aperture, although the
columellar edge is thicker and better developed.
34 . Umuersity of Michigan
The specimens show considerable variation in size; from
individuals seen in copulation, it appears that the males are
usually smaller and less globose than the females. Extremes
measure:
Altitude Greatest diameter Heightaperture Diameter aperture
12.4 mm. 107 (13.3 mm.) 55 (6.8 mm.) 63 (7.8 mm.)
9.3 mm. III (10.3 mm.) 62 (5.8 mm.) 66 (6.1 mm.)
9.I mm. 117 (10.7 mm.) 67 (6.1 mm.) 73 (6.6 mm.)
The color variation in this lot may be divided into the fol-
lowing classes, which do not appear to be related to habitat:
(a) General coloration: from milky-white and yellowish-
brown to orange and wine-colored. ‘Ten specimens out of the
total number were uniformly light-colored, while 3 were uni-
formly wine-colored. In the former case, the colored bands
are certainly absent; in the latter, they may be obscured by
the dark ground-color.
(b) One broad, dark band, just above the greatest ventri-
cosity of each whorl, and reaching almost to the suture above
(42 specimens). This band is either orange or wine-colored,
and may be distinct or diffuse. Some of these specimens also
show the broken stripe of class (d), which forms a lower
margin to the one considered here.
(c) Two broad bands, with a light band between (3 speci-
mens). The second band is just below the greatest ventri-
cosity of the whorls, and varies in color with the other.
(d) A fine, broken stripe of colored dashes, at the position
of the lower edge of the band in class (b) and often present
at its lower border. Seventeen specimens have no other mark-
ing; it varies in color like the bands.
(e) A diffuse tint on the base which begins at the position
of the lower edge of the second band in class (c), but which
does not occur with it. Eight specimens have the band in
class (b) and this basal coloration.
Occasional Papers of the Museum of Zoology 35
Helicna (Tristramia) zephyrina elatior “von Martens”
Crosse and Fischer (1893).’—Eleven specimens from trees in
the lowland forests (H, I, b) and the savannah forests (H,
Ill, b) ; from the ground in the savannah forests (H, III, a),
and from the burnt areas (H, II, b). This is a rather well-
marked race of H. zephyrina, although it occurs with the
typical form. In shape it is practically identical with the more
northern H. chrysocheila Binney (1851), but the latter usu-
ally (not always) differs markedly in color and appears quite
distinct. At least at present, it appears best to retain elatior
as a race of zephyrina, which occurs with the typical form, and
simply approaches, in shape, the other species. Specimens
measure:
Altitude Greatest diameter Heightaperture Diameter aperture
12.1 mm. 103 (12.5 mim.) 49 (5.9 mm.) 53 (7.0 mm.)
11.2 mm. 94 (10.5 mm.) 47 (5.3 mm.) 55 (6.2 mm.)
10.6 mim. 100 (10.6 mm, ) 52 (5.5 mm.) 57 (6.0 mm.)
Helicina (Tenuis) tenwis Pfeiffer (1849).
H Iindent Pfeiffer (1849).
Hi. vernalis Morelet (1849).
Fifty-eight adults; from leaves of trees, vines and shrubs
in lowland jungle (H, I, b) and on ground (H, III, a) and
on leaves of shrubs and cacti (H, III, b) in the savannah for-
ests. The specimens vary somewhat in size; extremes measure:
Altitude Greatest diameter Heightaperture Diameter aperture
9.7 mm. 100 (9.7 mm.) 48 (4.7 mm. ) 55 (5.3 mm.)
9.5 mm. IOI (9.6 mm.) 54 (5.1 mm.) 60 (5.7 mm.)
7.7 mm. 107 (8.2 mm.) 61 (4.7 mm.) 66 (5.1 mm.)
1“Filatior’ as used by von Martens (1890) is a one-word descrip-
tion and not a name. This is the reason why he puts H. berendti Pir.
as if it were a synonym under another of his short descriptions, “exca-
vatoangulata.” When he actually wished to denote or name a sub-
species, he placed the name in italics and followed it by the name of
the author or the letter “n.’ Crosse and Fischer (1893) have since
changed some of these descriptions into true names, as, for instance,
in the present case.
36 University of Michigan
The considerable color variation, which seems not to be cor-
related with the habitat, may be classified as follows:
(a) General coloration: milky-white to yellowish (variety
delta of C. and F. (1893) and typical linden), greenish (most
common), and chestnut-brown.
(b) One broad, brown stripe from near the greatest ventri-
cosity up to the suture (variety epsilon of C. and F.).
(c) Two broad, brown stripes, with a light stripe between ;
the second below the greatest ventricosity includes varieties
zeta and etta chiapensis (when combined with the brown body-
Colom) motC.vand sh
(d) Two dark and one light band above the greatest ventri-
cosity; the stripe of class (b) divided through the center
(variety gamma of C. and F.—typical tenuis).
Helicina lindent and H. tenuis were described in the same
paper (P. Z. S. 1848; April 25, 1849). The former name has
page priority, but von Martens (1890) chose to regard the
former as a form of the latter, so tenuis becomes the specific
mame. de vernahs Moreleh\(lest Noval) appeanse tome
prior as regards date of publication of the name, as his paper
bears the date Feb. 15, 1849. However, H. vernalis, like so
many of the names in the Test. Nov., is only recognizable
because later redescribed and figured, so it seems best to retain
Pfeiffer’s name. The same is true of H. amoena Pfr. and H.
purpureoflava Morelet, and of H. oweniana Pir. and H. coc-
cinostoma Mo.
Lucidella (Poenia) lirata (Pfeiffer) (1847)—Kighty-one
specimens in and at edge of pools, on ground, in lowland jungle
(H, 1,:a, or H, v, a).* This species appears almost semi-
aquatic, and is often found together with aestivating Pisidium,
Planorbis, etc.
Occasional Papers of the Museum of Zoology 27)
AMNICOLIDAE
Amnicola guatemalensis Crosse and Fischer—Very numer-
ous, under bits of lava and pumice, on the north shore of
Lake Catemaco, and also on the opposite side of the lake, in
shallow water near a sulphur spring (H, vu, d). These speci-
mens are narrowly imperforate to almost rimate. The original
description does not mention the microscopic, raised, spiral
lines; these are not very evident on the adults, but are very
noticeable in the young specimens. The operculum is thin,
corneous, and from dark brown to almost black in color. It
is three-quarters spiral, with evident, raised ridges parallel to
the growth-lines. The radula is shown in figure 5. In certain
lights, the outer tooth may be seen to be striated longitudinally
for almost its entire length.
Potamopyrgus coronatus (Pfeiffer)—A_ single specimen
from the Laguna de Chacalapa, a large savannah pond (H, vi).
AMPULLARIIDAE
Ampullaria flagellata Say (1827).
A. malleata Jonas (1844).
A. malleata, var. exculpta C. and F. (1890) .
A. malleata, var. arata C. and F. (1890).
Twenty specimens. Some of the shells from the larger for-
est pools near La Laja (H, v, a) are quite typical of what is
often cited as A. malleata Jonas. A. flagellata represents a
shell with a slightly more flaring lip than is general, but is not,
I believe, even subspecificly distinct. Two of the shells are
close to the figures of arata—1. e., they practically lack the
malleation. The term exculpta appears to include the more
malleated forms and does not appear even racially distinct.
All of the shells in this lot are rather small; the largest
measure:
Altitude Greatest diameter Heightaperture Diameter aperture
50 mm. 87 (43.5 mm.) 71 (35.7 mm.) 52 (25.8 mm.)
47.5 mm. 88 (41.7 mm.) 76 (36.1 mm.) 57 (26.7 mm.)
38 University of Michigan
The jaw-plates and the radula (fig. 6) are almost identical
with those cf A. flagellata belizensis C. and F., as figured by
the authors (1890), although their figure of the jaw, in par-
ticular, appears slightly idealized. Especially noteworthy are
the small size and sharpness of the cusps of the central tooth
and the broad and markedly double base of the second lateral.
The latter is represented from a slightly different viewpoint
in C. and F.’s figure of belizensis. In a few of the central
teeth of the three specimens examined the first of the lateral
cusps was double, and in many the outer cusp was double, so
that in a few cases aS many as II cusps were found on a
single tooth. A single inner lateral, in which the inner of the
two small, outer cusps was divided, was also noted, while
there was a quite constant tendency for a third cusp to be
differentiated from the cutting edge outside of the other two.
Ampullaria flagellata, subspecies erogata Crosse and Fischer
(1890).—Thirty specimens. Ampullaria seems to have a
peculiar ability to mature at almost any size. In places where
the shells are abundant, specimens two centimeters in length
have been seen in copulation. This was also noted in a Vene-
zuelan species. These small shells may or may not assume |
the adult characters, so that those that do have a thickened
peristome and a quite different shape from those that do not.
These small specimens are never markedly malleate, as the
malleation is not well developed except in the older shells.
The shells from the smaller, more temporary pools, espe-
cially from those in the burnt-over areas (H, V, b), appear
never to reach a large size, and thus form a quite well-marked,
ecological subspecies, which appears to fit the description of
A. erogata Crosse and Fischer very well. A. ceraswm Hanley
is not very different, and may be a similar form, perhaps of
another species. Examples of A. f. erogata measure:
Occasional Papers of the Museum of Zoology 39
Altitude Greatest diameter Heightaperture Diameter aperture
32.2 mm. QI (29.3 mm.) 72 (24.8 mm.) 53 (17.1 mm.)
24.6 mm. QI (22.4 mm.) 78 (19.2 mm.) 52 (12.8 mm.)
Ampullaria patula Reeve (1856),' catemacensis, new
subspecies
Figs. 2, 3, 4 and 7
Twenty-five specimens from Lake Catemaco (H, vii, d).
Shell thin, translucent, rimate; ground-color yellowish to
olive-green or dark brown (rich amber by transmitted light),
with 25 to 40 darker brown, spiral bands or lines of varying
widths, sometimes with a broadish band of creamy yellow
just below suture; surface marked with fine growth-wrinkles,
crossed by regularly spaced, delicate, more or less beaded
wrinkles, 2 to 3 mm. apart, and by microscopic, wavy ridge-
lets, so as to give the shell a beaded appearance under the lens ;
spire very low (somewhat eroded and pitted at very tip);
whorls 4 or 5, rapidly expanding, more or less flattened above,
_each with the sutural edge sloping up over the preceding whorl
so as to give, with the sharply marked, somewhat undulate
suture, the impression of being flattened over it; last whorl
greatly inflated, so as often to about equal in diameter, as
viewed from above, all of the others combined; aperture very
large; peristome slightly thickened within, but with edge
1Dr. Bryant Walker, to whom I sent the accompanying figures of
this form, writes: “Your figure certainly looks very much like Reeve’s
patula. Curiously enough, Sowerby in his recent revision of Ampul-
laria (Pr. Mal. Soc., VIII, p. 345) seems to have omitted any refer-
ence to it. I have four lots in the collection labelled ‘patula’ One
from the Amazon has got misplaced and I have not been able to find
it. The other three evidently belong to the same species, whatever it
may be. One lot from ‘Brazil’ are dealer’s specimens, and I know
nothing of their history. The other two came from New Granada.
They come from Rolle. The ‘typical’ form is banded and has the
interior dark brown, but the aperture is not so expanded as in your
shells, and the apex is higher than in Reeve’s figure. The largest
specimen measures 30.5x25 mm.; tip of apex eroded.”
40 University of Michigan
sharp, often somewhat expanded externally ; columellar margin
whitish to orange in color, and reflected so as to further close
the umbilicus; inside of aperture infuscate with chestnut,
darker towards edge, with the bands showing through, and
with the upper portion lighter and often whitish near the
suture. Operculum (figs. 3 and 4) horny, thin, pear-shaped,
dark-brown in color (smoky amber by transmitted light), and
considerably smaller than aperture; outside concave, dull and
marked by growth-lines externad to the submarginal nucleus,
or even laminating into thin layers at the edges; internal mar-
gin sigmoid with vertical, crescentic boss above the nucleus ;
inner surface with fine, radiate, subspiral striations; muscle-
scar dull and of same shape as operculum, not extending
internad to nucleus; extranuclear portion with smooth, shiny
deposit, which often obscures the radial lines.
Shell very variable in shape; some specimens are not shoul-
dered but globose, with the last whorl descending, so as to
raise the spire considerably above the aperture, the latter not
greatly expanded. Two color-forms were obtained, as indi-
cated above. One has the ground-color light olive-green,
shading to creamy yellow near the suture; the other has it
chestnut-brown, shading to smoky golden near the suture. The
first form was obtained from the shores of a rocky island in
the main lake, the second in a small but very deep body of
water in a subsidiary crater-cone, with the water surface about
100 feet in diameter. This small body of water was separated
from the main lake by a rock ridge about 60 feet high and
300 feet wide. More variation in shape was apparent in the
small number obtained of the first form. The type (fig. 4)
belongs to the second form.
This 1s a very distinct shell for an Ampullaria, although it
appears to belong to the A. ghiesbrechtit group. In the
Occasional Papers of the Museum of Zoology AI
Wheatley Collection, at the A. N. S. P., are two shells labeled
A. patula Reeve, Mexico, which are smaller specimens of the
brown color-form. The original description and figure of
Reeve fits quite well the light color-form, but none of my
specimens are completely imperforate, although the young
specimens are more nearly imperforate than the larger ones.
This subspecies appears to be a considerately larger shell than
Reeve’s patula. One young specimen is of about the same size,
but is quite different in shape, as shown in the table of
dimensions.
Greatest Height Diameter
Altitude diameter aperture aperture
Patula 30 98(29.5) 83(25.0) 62(18.5)2
Catemacensis
Young 36.5 88 (32) 82(30) 58(21)
Fig. 2 44.0 102(45) 89(39) 69(30.5) (type)
51.5 91(47) 77(39.5) 56(29) (not shouldered)
42 98 (41) 91 (38) 64 (27)
Mean 44.5 05 84 62 (24 adults)
Extremes 40-51.5 QI—102 77-91 56--69
The jaw-plates of this form are quite like those of A. flagel-
lata or of A. flagellata belizensis, although none of my speci-
mens were as regular nor had as well-defined cutting edges as
those shown in the figure of F. and C. (1890). The radula of
A. patula catemacensis (fig. 8) is very similar, but shows minor
and apparently quite constant differences (5 radulae exam-
ined). The middle cusp of the central tooth is much larger
and is not so sharp and angular; the lateral cusps are also
larger and better defined, and are spatulate in shape, while
those of flagellata are more nearly triangular. These lateral
cusps do not appear to have the tendency to split up into
smaller cusps, as noted under the latter species. The first
1The original description gives no dimensions; these taken from
figure.
42 University of Michigan
lateral differs in much the same manner as does the central;
like A. flagellata, three ectoconic cusps are often present. The
second lateral (or first marginal) is more slender, is ligulate
in shape, and is not double at the base, although there is a
thinner portion (uncalcified?) extending laterad from the
main, thickened portion. The outer tooth is also more slender
and the base is not so enlarged as in flagellata.
APEROSTOMIDAE
Aperosioma dysoni (Pfeiffer) —Eighteen specimens: from
the burnt-over area (H, II, b, dead shells) ; and from leaf-
humus in the lowland jungles (H, I,a). The largest specimen
measures: altitude, 15.8 mm.; greatest diameter, 129 (19.1
mm.) ; height aperture, 69 (11.0 mm.) ; diameter aperture, 65
(10.2 mm.).
The radula and jaw-plates of this species were examined;
they have been figured by Crosse and Fischer. (1888, 1890).
They also figure what they term “elements” in both this species
and in Tomocyclus simulacrum. In my specimens, these “ele-
ments” look as if they were the cells, or that each one was
the product of a single cell, and they are not regular in size
throughout the plate. ‘Toward the edge they are longer, and
are lanceolate to long trapezoidal in shape, while toward the
center they are more nearly square or, more often, polygonal.
The arrangement of these elements causes the apparent stria-
tions, seen under low magnification; this loses its regularity
when examined closely.
Cyrtotoma mexicanum salleanum (von Martens) (1865 ).—
Eleven adults and 6 young shells from under leaves in humus
in the lowland forests (H, I,a). These shells are quite typical
of salleanum (fig. 9), which apparently is the more general
form of the species in the favorable, damp habitats, as will
be discussed more fully under the form mexicanum. These
Occasional Papers of the Museum of Zoology 43
specimens are yellowish horn-colored, shading into amber
toward the tip. The growth-wrinkles are very regularly and
evenly spaced. The following extremes show the variation in
size of the adults:
Altitude Greatest diameter Height aperture Diameter aperture
Fig. 9 14.5 138 (20) 72 (10.5) 66 (10.5)
Largest 16.5 152 (25) 64 (10.5) 61 (10.0)
The jaw-plates of this species are practically the same as
those of Aperostoma dyson (Pfr.). The radula (fig. 8) is
also quite similar, but differs in several minor particulars. The
central tooth in C. mexicanum is more elongate and the cusps
tend to be somewhat more rounded than in the latter species.
The outer cusp of the second lateral is almost vertical and
faces inward. In the ordinary position of the tooth it appears
as simply a blunt, vertical projection on the outer margin. of
the tooth, but when seen in profile it appears more prominent
than in 4. dyson, and projects out almost at right angles to
the remainder of the cusps. The outer tooth has three cusps,
as in A. dysont, but lacks the attenuate point in the lower cor-
ner. In both A. dysoni and the present species there is not a
definite base to this last tooth, as might be judged from Crosse
and Fischer's figure, but the entire tooth forms a plate with
three cusps on the inner side. The inner and central cusps
curve inward and down, but the large, triangular, basal cusp
faces directly inward. The tooth appears to be attached to
the basal membrane by its outer edge.
Cyrtotoma mexicanum mexicanum (Menke) (1830)—One
adult (dead shell) from the burnt-over region (H, II, b), and
6 adults and 2 young specimens from the strip of jungle along
the upper portion of La Laja. These last woods are about
intermediate in type between the lowland forests (H, I, a)
and the savannah forests (H, III, a).
This set of specimens presents evidence that mexicanum and
44 University of Michigan
salleanum are ecological growth-forms of the same thing.
According to von Martens (1890), the only trustworthy dis-
tinctions between the two are the larger size of salleanwm and
the peristome. He describes the latter as follows: “lower lobe
of the columellar margin beneath the deep notch is always free
in C. mexicanum and soldered to the penultimate whorl in C.
salleanum; this seems to be a constant character.”
The newly formed peristome of this species 1s smooth on
its outer surface and is usually regularly attached to the body
whorl, although some specimens (for example, F. and C., /. c.,
pl. xxxv, 4; also’ Specimens in) the (A. NESS) E>) apparently;
have a slight scalariform tendency. Under the most equable
conditions of the environment, this condition of the peristome
is apparently retained; so that in the lowland forests all of the
specimens are quite typical of salleanum (fig. 9). However,
the size cannot be used as a specific character; although the
specimens of salleanum tend to be somewhat larger, the small-
est specimen obtained (20 mm. in diameter) belongs to this
form.
The differentiation of C. mexicanum mexicanum from this
type is apparent in the specimens from along La Laja. In
these drier habitats there appears to exist a tendency to pro-
duce the reflected peristome when smaller in size (younger ?).
Probably on acount of the repeated periods of aestivation,
additional layers of material are secreted over the outside of
the peristome, as shown in the figures (figs. 10, 11 and 12).
These additional layers are most extensive on the palatal and
basal portions and tend to widen the peristome as well as
increase its thickness (fig. 10). On the columellar margin,
the added layers fail to attach themselves to the penultimate
whorl (fig. 11), so that finally the typical mexicanum is formed
(fig. 12), in which the lower lobe of the columellar margin is
Occasional Papers of the Museum of Zoology 45
not adnate to the body whorl. If this process should be con-
tinued long enough, I have no doubt it would result in the
complete freedom of the peristomal margin.
The shells of the form mexicanum are more variable in
appearance than are those of salleanum. ‘The growth-wrinkles
of the former are quite irregular, and the epidermis is usually
eroded toward the tip, which may be somewhat chalky in
appearance. Specimens measure:
Altitude Greatest diameter Height aperture Diameter aperture
Smallest 14.5 145 (21) 66 (9.5) 69 (10)
Fig. 10 17.0 135 (23) 65 (11) 65 (11)
Fig. 11 15.0 149 (23) 65 (10) 68 (10.5)
Fig. 12 15.0 150 (22.5) 67 (10) 70 (10.5)
Part III. ZoNrITiIpDAE AND HELICIDAE
ZONITIDAE
Guppya gundlachi (Pfeiffer) (1840)—One hundred three
specimens; on ground among humus and decaying leaves in
the lowland forests (H, I, a); and a few feet above ground,
on young palms in the lowland forests (H, I, b) ; on elephant-
ears along Arroyo Hueyapam (H, II, a), and on cacti in the
savannah brush (H, III, b). Apparently, it is a ground spe-
cies, which moves up into the lower vegetation in the wet
season.
As the dried animals were still in some of the shells, two
preparations of the jaw and radula were made and examined.
The jaw (fig. 3) is quite similar in structure to that of Huconu-
lus, but has a more nearly semicircular outline. The formula
of the radula (fig. 1) may be expressed:
I 5 242 I
C—;L—;M—-+ — + —;3 or 27-5-1-5-27.
$ 3 3 + I
The central has broader and shorter cusps than Euconulus.
The first four laterals are practically the same shape as the
central; in fact, I could not determine which was the central
46 University of Michigan
until after counting the laterals. The fifth lateral is turned
considerably inward, and is almost completely hidden by the
distal end of the first marginal. The break to the marginals
is a sharp one, and shows as a raised edge, even under low
magnification. The well-developed marginals are all tricuspid
and point obliquely inward, and the transverse row itself also
slopes obliquely backward (1. e., in the direction towards which
the cusps point). As the inner cusp of each marginal overlaps,
_to a certain extent, the outer one of the preceding tooth, it is
sometimes difficult to make out more than 2 cusps, which prob-
ably accounts for Binney’s statement that only a portion of
the marginals are tricuspid. The lenses in his time were con-
siderably inferior to the modern oil-immersion objective.
Amongst the outer reduced teeth, the thirtieth and thirty-first
have four cusps each, while the outermost is a mere denticle,
and is lacking in some of the transverse rows.
For comparison, the jaw and radula (fig. 2) of Guppya
sterkii (Dall)? was also examined. This species, as Vanatta
(1920) has already pointed out, has a similar dentition to that
of G. gundlachi, only the radular ribbon is so minute as not
to fill the field of the oil-immersion objective. ‘The central
tooth, for instance, is only about 4 microns (.004 mm.) in
I 5 13-15
width. The formula is approximately: C—;L—;M
3 3 3
The number of cusps out to the ninth marginal was determined,
but their shape on this tooth could not be made out very accu-
rately, as the ends of the cusps are smaller than the limit of
possible microscopic vision, and so could only be detected as
1 Dried animals; A. N. S. P. No. 46177; collected at the Clydesdale
Brick and Stone Company Farm, Beaver County, near Elwood City,
Paiby jee Clark
Occasional Papers of the Museum of Zoology 47
points of light. For the same reason, the number of cusps on
the outermost marginals, and perhaps the exact number of the
teeth themselves, is indeterminable without resort to ultra-
microscopic methods. On the first radula, in which the basal
membrane disintegrated while under examination, so that the
teeth spread out quite evenly in all directions, 1 thought I
could count 15 marginals, in the other but 13. All of the inner
teeth are quite of the same shape as those of G. gundlachi.
The jaw is also very similar in the two species, but that of
G. sterkit is even more nearly semicircular in outline.
Guppya gundlachi, subspecies orosciana von Martens (1892).
—Two specimens, found in humus among rocks near Laguna
de Catemaco. This mountain subspecies agrees with typical
gundlacht in the prominence of the spiral lines and in general
shape, but differs in the marked carination of the last whorl.
However, specimens with a distinct angulation were also found
in the lowlands (H, I, a) among those with more rounded
whorls.
Guppya (Habroconus) trochulina (Mo.) (1851).
Helix selenka: Pieiffer (1866).
Thirty-four specimens ; adults on leaves of palms and trees,
in lowland forests (H, I, b) and in savannah forests (H, III,
b); juvenile specimens from elephant-ears along Arroyo
Hueyapam (H, IH, a); and one dead specimen from humus
amongst rocks near Laguna de Catemaco. An arboreal species
found with Helicina, Drymaeus, and Oxystyla.
The jaw (fig. 5) and radula of this form were also examined
from two dried animals. The jaw is very similar to that of
the general group. The formula of the radula (fig. 4) is:
I II 1S. TO S35) O-2
Og eg WE = Se
3 3 2 3 + I
or (48, 45)-11-1-11-(48, 45). The proximal portion of the
.
J
48 University of Michigan
reflected edge of the central is particularly elongate, and the
mesocone is also slender and lanceolate. ‘The first lateral is
turned slightly inward and the entocone has moved up on the
outside of the mesocone. Both of these characters increase
in prominence through the series of laterals, until in the elev-
enth tooth the entocone is very small and is high up on the
outside of the mesocone. This tooth is shaped very much
like what may be termed the first marginal, only the latter is
bicuspid. The first 18 marginals are bicuspid, and arranged
in an almost horizontal row. The individual teeth (No. 21 is
typical) are not so obliquely placed as are the tricuspids of
G. gundlachi, or those of this species. T he thirtieth tooth shows
a minute, additional cusp outside of the others, and is the first
of 19 tricuspids. With these, the transverse row begins to
curve obliquely backward. These tricuspid teeth are even
larger and better developed than are the bicuspids. ‘With the
reduction in size of the outermost teeth comes an additional
cusp on the forty-ninth, which is the first of 8 or 9 quadricus-
pids of rapidly reducing size. The two outer denticles, which
are often absent (even in adjacent rows in the body of the
radula this much variation was noticed), are practically
cuspless.
Euconulus (?) pittieri (von Martens) (1892).—One dead
specimen from humus among rocks, near the Laguna de
Catemaco. This specimen agrees very well with the original
description. It differs from £. elegantultPby the marked cari-
nation of the whorls, the more conical shape, the greater prom-
inence of its radial wrinkles, which extend to within one whorl
of the apex and which, in regularity and prominence, are some-
what reminiscent of Strobilops, and the coincident relative
obscurity of the spiral striations, which, however, are quite
noticeable on the lower side. It differs from G. gundlachi
Occasional Papers of the Museum of Z oology 49
orosciana by its greater altitude and by the character of the
sculpture, as just described.
Euconulus elegantulus (Pilsbry) (1919).—Two hundred
twenty-eight specimens; on ground in lowland forests (H, I,
a) and savannah brush (H, ITI, a) ; the most abundant species
on the elephant-ears along Arroyo Hueyapam (H, II, a); and
on leaves of low vegetation in the lowland forests (H, I, b).
Apparently a ground species, which moves up into the lower
vegetation, somewhat more so than does Guppya gundlachi,
but not truly arboreal in habits, as is G. trochulina.
The jaw and radula (fig. 6) of two dried specimens of this
species were also examined. The jaw is very similar to that
of E. fuluus. The formula of the radula is:
I ) A) B 3-4 O-I
Game 5 yep Me ee ee
3 3 2 3 4 i
or (31, 33)-9-1-9-(31, 33). The central has the reflected
plate shorter distally than in G. trochulina, but the cusps are
longer, so that the whole tooth appears equally elongate. The
laterals differ in the same manner, but go through similar
changes to those in the latter species, and the break between
the last tricuspid tooth and the first bicuspid is but little more
marked. The main difference between the two species lies in
the fact that all of the well-developed marginals are bicuspid
in E. elegantulp? and the rows are more nearly horizontal than
in G. trochulina. Two tricuspids and 3 or 4 quadricuspids
occur among the reduced teeth at the outer end.
’
For comparison with this species, the radula of Euconulus
fuluus (Miller) was re-examined.1 The shape of the teeth,
as very well shown in Taylor’s reproduction (1908) of Schep-
1Two large specimens; A. N. S. P. No. 87302; collected at Buck-
field, Oxford County, Me., by J. A. Allen.
50 University of Michigan
mann’s figure, are practically identical with those of &. ele-
gantulus, ‘The maximum formula is:
I LO HZOn FA wees I
C—;L—;M —-+ — + — + —; or 28-10-1-10-28.
3 3 2 3 4 I
The count for the laterals was the same for the two specimens
examined, but the marginals were determined in only one, as
the other curled under at the edges. The divergence between
the descriptions of various writers depend probably in part on
the inconspicuousness of the entocone on the laterals (in the
tenth it appears as simply a point of light high up on the
mesocone) and the difficulty in counting the extreme marginals,
especially as the edges have a tendency to curl under. The
outer denticles also vary in numbers; I have found differences
of two teeth in adjacent rows. All of the well-developed mar-
ginals are bicuspid as in £. elegantulus.
Among others that need not be discussed here, the follow-
ing group names have been applied to our American species
of this general group:
Stenopus Guilding (1828), not of Latreille (1825).
Conulus Fitzinger (1833), not of Rafinesque (1814).
Guppya Moerch (1867). Type Conulus vaccus “Guppy”
Moerch (1867), obviously a misprint for Conulus vacans
Guppy (1866).
Habroconus Crosse and Fischer (1872). Type Helix selen-
kai Pfr. (1866).
Euconulus Reinhard (1883). Type Helix fulva Muller
(1774).
Discoconulus Reinhard (1883). No type given, but H.
gundlachi Prf. is mentioned as an example.
Ernstia Jousseaume (1889). Type Ernstia ernsti Jouss.
(1889).
Occasional Papers of the Museum of Zoology 51
Spiroconulus von Martens (1892). Type H. gundlachi Pfr.
(1840).
Conulus vacans Guppy, from Trinidad, is thus the type of
the first usable name, Guppya. It is a form which is appar-
ently closely related to Guppya gundlachi, but is somewhat
larger. Young (?) specimens from Venezuela (Tate, collec-
tor) in the A. N. S. P., labeled as vacans, are very. close to
gundlachi, but have somewhat coarser whorls. These speci-
mens have 34 whorls with practically the same diameter as
adult G. gundlachi with 5 whorls. Guppy (1866) describes
the caudal projection, the marked spiral striation, and the
radula. |
The description of the last is: “Lingual teeth about 30.5.0.
5.30, broad, subequal, central obsolete; first five laterals sym-
metrical with a large rounded cusp having a smaller cusp of
similar shape on each side; outer laterals bicuspid, resembling
the teeth of Testacellus.” His supposition that the central is
obsolete is doubtless due to the difficulty of its identification.
The description of the laterals agrees with those of G. gund-
lachit. Due to the overlapping of the marginals, as already
pointed out, these would appear bicuspid under the microscope
available in 1866.
Spiroconulus von Martens, type G. gundlachi, thus becomes
a synonym of Guppya, which is not Guppya s. s. of von Mar-
tens (1892). According to Pilsbry (1910), Ernstia is also a
synonym. From the shell characters of the specimens I have
seen, I think it likely that G. biolleyi von Martens (1892) will
also be found to belong in Guppya.
Helix selenkat is a synonym of Helix trochulina Morelet
(1851), so the species of which the radula has just been
described may be considered as typical of Habroconus, which
is used here as a subgenus of Guppya. From the shell char-
52 University of Michigan
acters, Guppya championi von Martens, G. browni Pilsbry, and
G. costaricana Pilsbry, with the variety elatior Pilsbry, appear
to belong in this group. All of these species are large shells
with weak spiral and radial striation and rather rapidly
increasing whorls.
On the basis of the radula alone, Euconulus would certainly
become a subgenus of Habroconus, and the latter would be
separated genericly from Guppya. However, Crosse and
Fischer (1872) remark: “After M. Bland (in letter), it fol-
lows from a verbal communication made to him by Dr.
Berendt, who had occasion to examine in living state Helix
selenkai, that that mollusc possesses, at the posterior extremity,
a mucous pore quite (tout ad fait) close to that of Stenopus”’
(translation). This appears to indicate a closer affinity with |
Guppya, although Euconulus also has a mucous pore.
In addition, Euconulus is a Holarctic genus, and in general
the American forms decrease in size towards the south. (From
the shell characters, I think it probable that G. micans Pilsbry
and G. jalisco Pilsbry also will be found to belong in Euconu-
lus.) Guppya, on the other hand, is a neotropical genus, whose
forms (for example, G. vacans, G. gundlachi and G. sterkii)
tend to decrease in size toward the north—that is, in the oppo-
site direction. This appears to indicate a northern center of
origin for Euconulus and a southern one for Guppya. Habro-
conus only has, as far as known, neotropical species, which
are larger than any of the American forms of Fuconulus.
For these reasons, Habroconus is tentatively used here as a
subgenus of Guppya, while the more familiar Euconulus is
retained as a genus to include the conical forms with better
developed radial striations, and with all of the well-developed
marginals bicuspid. From the shell-characters, I rather doubt
if the acutely carinate species with practically no spiral stria-
Occasional Papers of the Museum of Zoology 53
tions (example G. calverti Pilsbry) will be found to belong to
any of these groups in its strict sense.
In the radulae examined of these three groups, Guppya,
Habroconus, and Fuconulus, three more or less distinct ten-
dencies or trends seem to be present.
1. A’tendency for all of the teeth to become elongate and
for the outer teeth to turn inward and to lose the ectones. The
marginals of all three groups have lost the ectones, but the
central and laterals of Guppya s. s. have not been affected to
any great extent. Both the centrals and the laterals of the
other two groups are elongated, although in Habroconus this
is accomplished by the increase in size of the distal portion of
the reflected edge, while in Euconulus the cusps themselves
have been lengthened to a greater degree. The laterals of
beth of the last two groups show a progressive tendency, from
the center out, for the ectocones to move up on the outside of
the mesoccnes and finally to diminish in size.
2. A tendency for the ectocones to be reduced in numbers.
This has not affected Guppya s. s. as much as the others, as all
_ of the marginals have at least two ectocones. Half of the well-
developed marginals of Habroconus still retain two ectocones,
while none of the large marginals of Euconulus have more
than one. The bicuspid teeth tend to move back into a less
oblique position than that of the tricuspid. This tendency
towards reduction of the number of cusps on the marginals
is carried still further in such genera as Zonitoides, where the
definitive marginals are mostly unicuspid.
3. A separate tendency, at least somewhat coincident with
size, to reduce the number of teeth in the transverse rows.
Thus, the largest species, G. trochulina, has about 119, E. ful-
vus about 77, &. elegantulus about 85, G. gundlachi 65, and G.
sterki 41. Up to a certain point, this appears to go on more
54 University of Michigan
or less equably throughout the radula, and probably accounts,
in part, for the lack of transitional teeth between the laterals
and marginals in both species of Guppya s. s.
Zonitoides (Pseudohyalina) minuscula (Binney ).—Eight
specimens from humus, and on the underside of leaves and
bits of bark on the ground, in the lowland (H, I, a) and the
savannah (H, III, a) forests.
HELICIDAE
Thysanophora plagioptycha (Shuttleworth) —Fight speci-
mens from leaves and humus in the lowland forests (H, I, a).
Thysanophora pilsbryi, new species
Figs. II, 12, 13, 14
One specimen from humus in the lowland forest along La
Laie, Cal, il, 2))c
Shell minute, depressed, whitish horn-colored; whorls 3%,
gradually increasing in size; last whorl descending slightly, so
that the upper edge of the aperture is at about one-half the
height of the preceding whorl; margin of aperture simple, thin,
and almost circular in outline as far as complete; suture well
marked, impressed; greatest diameter of whorls considerably
above middle; umbilicus large, almost one-third the diameter
of the shell, and showing all of the whorls; sculpture of shell
consisting of equally spaced, quite regular, delicate riblets,
which run parallel with the growth-lines, extend to within one-
quarter of a whorl from the apex, and are highest on the upper
side of the shell; entire surface of the shell, as far as could
be made out, also covered with delicate striatulations, which
cross each other at right angles, but cross the growth-lines at
oblique angles, and form minute but extremely regular squares
4 microns (.004 mm.) across. This minute sculpture is regu-
lar and uniform in spacing from near the apex to the edge of
the last whorl (fig. 11). Measurements: altitude, .71 mm.;
Occasional Papers of the Museum of Zoology 55
greatest diameter, 1.30 mm.; lesser diameter, 1.19 mm. ; height
aperture, .47 mm.; width of aperture, .47 mm.; greatest diam-
eter of umbilicus, .43 mm.
This minute species appears from its shell characters to be
most closely related to Thysanophora tater Pilsbry, and so
belongs within the limits of the genus as at present constituted.
It differs from that species by its much smaller size, by the
gradually increasing whorls, and by its fine and regular striatu-
lations. Under high magnification (700 diameters) all shells
show some structure, which is perhaps caused by the edges of
the crystals of which it is composed, but these are the most
regular that I have ever examined. They are very much more
regular and delicate than those of the Striatura-group of the
Zonitidae.
In order to differentiate this species more exactly, and to
show its relations to the other Mexican and Central American
forms, the following key is presented, which includes all of
the species usually placed in Thysanophora, which have been
listed from that district. I have examined under rather high
magnification (at least 250 diameters) all of the forms included,
with the exception of H. guatemalensis C. and F. and T. tur-
binella (Mo.). ‘The position of these two forms in this key
is doubtful, as their descriptions do not accurately describe
the shell sculpture.
A. Apical whorls spirally striate, without definite markings (Radio-
discus?). 1.84; 63; 3%. coloba Pilsbry
AA. Apical whorls with irregular punctations, somewhat radially
arranged. Lower whorls also with irregular punctations, with
1The numbers for each species indicate in the order given: first,
the greatest diameter in millimeters; second, the height-index in per-
centages, which is taken as the height divided by the greatest diameter ;
and last the number of whorls. The greatest diameter is taken as a
basis for the index, as this dimension is usually most accurately deter-
mined in small species.
56 University of Michigan
tendency to be arranged in diamond-shaped patterns; and with
regularly spaced, much larger, papilla-like bosses, arranged in a
definite pattern so as to form rows more oblique than the growth-
lines and also rows less oblique. Large shell with concave apex.
TO) cbske Al, sigmoides (Mo.) (wvitrinoides Trm.)
AAA. Apical whorls with cuticular riblets, more oblique than, and
crossing, the growth-lines.
B. Oblique, cuticular riblets over entire shell.
C. Whorls rounded.
D. Most elevated forms; cuticular riblets tend to die out on
body whorl. 2.5; 112; 5. rhoadsi Pilsbry
DD. Not quite so elevated; about as high as wide.
E. Umbilicus minute, rimate; suture less deeply impressed.
3; 100; 4.
caecoides (Tate) (granum Strebel, guatemalensis C. and F.)
EE. Umbilicus larger (10-11 in diameter) ; suture more deeply
impressed. 2.8; 100; 4%. plagioptycha (Shuttleworth)
DDD. More depressed species; umbilicus larger (less than 7
times in diameter.
F. Smallest species: 2.55; 84; 4.
fuscula (C. B. A.) (fischeri Pils.)
HES ie ancens 77 Osn4uee proxima Pilsbry
FFF. Largest: 4.6; 83; 434. canalis Pilsbry
CC. Conical shell; last whorl subangulate.
G, Ilavreeres 2 eos 8: _ turbinella (Morelet) ??
GG. Smaller: 4.5; 78; 5 paleosa (Strebel)
BB. Oblique riblets represented on last whorls by oblique rows of
crescentic projections; shell discoid.
- (Thysanophora s. s.) conspurcatella (Morelet)
AAAA. Apical whorls with wrinkles or riblets parallel to growth-
lines.
H. Apical whorls also with rather indistinct spiral striations, which
tend to give the radial wrinkles a beaded appearance.
I. Lower whorls with rather distant, long, hair-like processes,
arranged so as to form a diamond-pattern with oblique rows
crossing the growth-lines, both more and less obliquely.
K. Smaller and more elevated: 2; 90; 6. intonsa Pilsbry
KK. Larger and discoid: 4; 62; 4 kornit (Gabb)
II. Without hair-like processes, as far as observed.
L. Entire shell with fine, close-set and irregular, anastamosing,
radial wrinkles or minute riblets; spiral striation less well
marked.
Occasional Papers of the Museum of Zoology 57
M. Almost discoid in shape: 4; 62; 4. hornti (Gabb)
MM. More elevated spire: 4.5; 78; 5. wmpura ( Pir.)
LL. Entire shell with beaded appearance, a few of the radial
folds may be developed into higher riblets.
N. Shell larger and more depressed.
O. 3; 83; 4 (type Microconus). wilhelmi (Pfr.)
OO 3470 ae cockerellae Pilsbry
NN. Shell small; Pupisoma-like; texture like “fine woven
material.” 1.95; 100; 4%. textilis Pilsbry
HH. Apical whorls without definite spiral striations, but with regu-
larly spaced, smooth, well-developed riblets, parallel to growth-
lines.
P. Larger species; slight tendency towards spiral stri-
ations. 3; 60; 3%. tatet Pilsbry (blakeana Tate)
PP. Small species; minute striations between ribs,
which form oblique squares, 4 microns across.
NSS Ate Sie pilsbryi n. sp.
Averellia (Trichodiscina) coactiliata (Ferussac) (1838) .—
Seven specimens; from leaves and bark of trees in lowland
jungle (H, I, b). One of these specimens contained the dried
remains of the animal, and from it the jaw and radula were
obtained.
The arcuate jaw (fig. 9) bears 13 broad, low ribs, but is
also striate so that the ribs appear rather irregular and indis-
tinct. The radular formula (fig. 7) is:
I 9 07) 4 I
>-L—;M— + — + —;3or 3I-I-31.
1-3 1 See 9) I
The central and the inner nine laterals are functionally uni-
cuspid, but the rather long and slender mesocone bears lateral
Cc
expansions or wings on both sides, below the level of its cut-
ting edge. In some of the centrals, each of these expansions
has a rather blunt and very indistinct cusp, which is only vis-
ible under the oil-immersion objective. (On other centrals I
was unable to detect these, and suspect that they are not always
58 University of Michigan
developed.) The expansions of the laterals are entire, except
that in one or two cases the outer wing was apparently slightly
angulate. A definite ectocone is developed on the tenth tooth,
but the entocone remains vestigial out to about the twelfth.
The teeth just beyond the tenth are more elongate and have
shorter bases than any of the others. The remainder of the
definitive teeth are tricuspid, but the outer ones are variable,
and may have as high as 5 cusps. The thirty-first is a mere
denticle.
Averellia (Trichodiscina) suturalis (Pfr.) (1846)—Two
young specimens appear to be this species; one from the
ground in the lowland jungles (H, I, a), the other under chips
of bark on the ground in the savannah forests (H, III, a).
Averellia (Miraverellia, new subgenus) sumichrasti (Crosse
and Fischer) (1872).—Five specimens: 1 adult, bleached shell
from the burnt-over area (H, II, a) ; 1 specimen (almost adult)
and a juvenile from under logs on the ground (H, II, a), and
2 juveniles from the bark of a tree (H, IJ, b) in the lowland
jungle.
This is a flattened, subangulate species, with the last whorl
sharply descending near the aperture, as in most species of
this genus. As Crosse and Fischer have pointed out, the whole
surface of the fresh specimens has low, but prominent, cres-
centic to lanceolate excrescences, which extend parallel to the
growth-lines. These are interspersed with more numerous,
minute, conical projections, so that the entire shell appears
setose under the lens. This sculpture reaches to the apex, but
is more minute on the apical whorls, so that they appear
smooth, by contrast, to the naked eye. These projections super-
ficially break the regularity of the growth-lines, so that the
epidermis appears marked with anastamosing wrinkles, which
Occasional Papers of the Museum of Zoology 59
give the shell much the appearance of some species of Thy-
sanophora. In the bleached specimen the epidermis is gone
and the growth-lines appear quite regularly parallel, but, under
a lens, the larger excrescences can be made out as compara-
tively slight, local developments of the growth-wrinkles. My
specimens appear to be slightly more flattened above the sub-
angulate periphery than in those figured by Fischer and Crosse
(1902). The largest specimen measures: altitude, 8.8 mm.;
greater diameter, 200 (17.7 mm.) ; lesser diameter, 170 (14.9
mm.).
In the specimen that was almost adult the remains of the
dried animal were found, and the jaw and radula were obtained.
The jaw (fig. 10) is broadly arcuate, has a central superior
angulation, and bears 11 low, broad, striate ribs. The cutting
edge has a transparent border, which is apparently much thin-
ner than the basal portion.
The radular formula (fig. 8) is:
I 7 26 2
C—;L—; M —— + — jor 36~-1-36.
Seo a anes eet!
The central tooth is comparatively broader than in A. coac-
tiliata, and is definitely tricuspid. The ectocone and entocone |
are borne rather near the tip of the mesocone, but are on the
same level or slightly above it. The first 7 laterals are also
definitely tricuspid. Beyond this, the teeth become more elon-
gate, and the entocone is often bifid. Beyond the twenty-eighth
tooth, the ectocone also is often double. The outermost teeth
seen are short, very variable, and multicuspid. There may
be a denticle or so beyond the outermost tooth detected, as
the outer portion of the basal membrane was lost, due to
trouble in mounting. Nevertheless, the vestigial character of
60 University of Michigan
the last teeth present show that they are very near the outer
edge of the radula.
These differences in the sculpture of the shell and in the
radula seem to warrant the separation of H. sumichrasti
Crosse and Fischer (1872) as the monotype of ‘a new sub-
genus, Miraverellia. The descriptions of the shell-sculpture
and of the radula, given above, separate this group from Tri-
chodiscina von Martens (1892), of which H. coactiliata Ferus-
sac (1838) is the type. The radula of Averellia Ancey (1887),
in the strict sense (type H. macneili Crosse, 1873), has not
been examined, but this typical subgenus is separated distinctly
from either of the others by the peculiar, lamella-like infold-
ings of the last whorl; the shell-sculpture is closer to that of
Trichodiscina.
Occasional Papers of the Museum of Zoology 61
PEATEs
The numbers of the figures are the same as used in the
dimension tables in the text. The scale of each plate is shown
on it, by means of a hair-line, which represents, in plates
I—XIII, an actual length of one centimeter. In the other plates,
the scale is indicated above each hair-line. All drawings were
made with the aid of a camera lucida.
62
University of Michigan
RAVE
Elliptio and Actinonaias. Young and depauperate specimens.
Figures 1 and 2. A. walkert. Young specimens.
Figure 3. E. plexus distinctus; juvenile.
Figures 4 and 5. &. plexus; depauperate race.
Figures 6 and 7. &. liebmanmi cuatotolapamensis; young.
T Ww 1d : STTHHS NVOIXAV
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iat
x
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STTHHS NVOIXa]
es
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Ga uiez
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ak y
ae
66 University of Michigan
PAE Dial
Elliptio. Hinge armature.
Figure 22. KE. liebmanni cuatotolapamensis. Hinge armature of
right valve of type (figure 22, plate IV).
Figure 15. E. plexus distinctus. Hinge armature of right valve
of figure 15, plate II. Young shell.
Figure 11. &. plexus distinctus. Hinge armature of right valve
of figure 11, plate II. Old shell.
MEXICAN SHELLS Pena JOU
1001.
68
University of Michigan
PLATE IV
E. liebmanni cuatotolapamensis. Variation.
Figure 22. Type specimen.
AI WV 1dg STTAHS NVOIXY,
ter ae
Pein
Pee
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Anodonta globosa nopalatensis.
EH eae 20.) iene ce inaannet
A awd STTAHS NVOIX
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Arete
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72 University of Michigan
Pi Val
Plagiola opacata. Male? (natural size).
Figure 35. Inner view of right valve, outer view of left valve, dor-
sal view, and hinge armature of left valve.
val
¥
4
7
PEAT
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XICAN SH
4
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76
University of Michigan
PAE Vile
Lampsilis and Actinonaias.
Figures 39-42. L. rovirosai sanjuanensis. (Figure 40 is type).
Figures 43-45. Arroyo Hueyapam shells, like A. umbrosa.
Bigures 46, 47. San Juan River shells, like A. explicata.
MEXICAN SHELLS PAG WILL
rae
pe
78
University of Michigan |
Pe Xe
Actinonaias walkeri. Type (natural size).
Figure 49. Dorsal and left views of male(?) shell.
MEXICAN SHELLS Pie IDX
80 University of Michigan
PLATE X
Actinonaias walkeri, Sexes (?).
Figure 48. Female (?) shell.
Figure 49. Type (male?) shell.
Figure 50. Male (?) shell.
MEXICAN SHELLS PLATE X
Sy
82 University of Michigan
PILATES, 2K IL
Lampsilis and Actinonaias. Hinge armature.
Figure 53. Lampsilis ruthvenit. Left valve of figure 53, plate XIII.
‘Figure 48. Actinonaias walkeri. Right valve of figure 48, plate X.
Figure 49. Actinonaias walkeri. Weft valve of figure 49, plates IX
and X.
MEXICAN SHELLS
PLATE
SS
raters ————
ss
LW
XI
. a Lg Y ~ ‘ \
nie MN r Shae
e4 University of Michigan
PLATE, XII
Lampsilis ruthveni (natural size).
Figure 53. Exterior view of left valve and hinge armature of right;
dorsal view of entire shell. Same as figure 53, plate XIII.
Prare XII
MEXICAN SHELLS
LIS
=
‘ie : yond i i
a |
NO me».
86
University of Michigan
PLAINS, SII
Lampsilis ruthveni (natural size).
Figure 52. Male (?) shell.
Figure 51. Type (female?) shell.
Figures 53, 54. Female (?) shells.
IX Ww Ig
STIEHS NVOIXayy
3
<
Ws)
88
University of Michigan
IRIN, DID
Helicina and Ampullaria.
Figure 1. Helicina zephyrina. Basal view with operculum in place,
as in aestivating individuals, to show the sinuation of the basal lip
and the crack left between the operculum and the lip.
Ampullaria patula catemacensis. Type specimen.
Exterior view of operculum.
Interior view of operculum.
Figure 2.
Figure 3. A. p. catemacensis.
Figure 4. A. p. catemacenstis.
MEXICAN SHELLS IPC As, DCW
Lees
go
University of Michigan
IPIL AINE, SOW,
Amnicola and Ampullaria. Radulae.
Figure 5. Ammnicola guatemalensis.
Figure 6. Ampullaria flagellata.
Figure 7. Ampullaria patula catemacensis.
MEXICAN SHELLS PLATE XV
92 University of Michigan
JEANIE, OWL
Cyrtotoma.
Figure 8. C. mexicanum salleanum. Radula.
Figure 9. C. m. salleanum. Aperture.
Figures 10, II, 12. C. m. mexicanum. Apparent stages in develop-
ment of aperture; drawn from different specimens.
MEXICAN SHELLS JPL NaS SOW TL
10mm
mh
eo
a
oan
Se
op
a
94 University of Michigan
PIES, WILL
All drawings are made with the aid of the camera lucida. The scale
of figures I, 2, 4, and 6 is given under figure 4, while that of figures
12, 13, and 14 is under figure 12. Each of the other figures has its
own scale. The laterals and marginals are numbered as a continuous
series, from the center out.
Figure 1. Guppya gundiachi; radula.
Figure 2. Guppya sterku,; radula.
Figure 3. Guppya gundlachi; jaw.
Figure 4. Guppya trochulina; radula.
Figure 5. Guppya trochulina; jaw.
Figure 6. Euconulus elegantulus; radula.
Figure 7. Averellia coactiliata; radula.
Figure 8. <Averellia sumichrasti; radula.
Figure 9. <Averellia coactiliata; jaw.
Figure 10. Averellia sumtchrasti; jaw.
Figure 11. Thysanophora pilsbryi; detail of sculpture.
Figure 12. Thysanophora pilsbryi; top view.
Figure 13. TJ. pilsbryt; front view.
Figure 14. 7. pilsbryi; under side.
MEXICAN SHELLS IPE atta, DOW UI
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