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From the Proceedings of the California Academy of Sciences, April 17th, 1876.

Description of a New Genus and Species of Decapod
Crustacean,

BY W. N. LOCKINGTON.
Family PINNOTHERIDZ.

Tubicola. nov ( yhnose Ec: l% WN XQ
cola. . gen. EMUUYS CO |

Carapace extremely broad; fourth pair of legs much elongated, fifth pair
rudimentary.

Habitat, the inside of the tube of an annelid.

ADIN IX2
Pubicola longipes. nov. sp.

Carapace broad, transverse, more than twice as wide as long; front occupying
about one-third of the width of the carapace; antero-lateral margins broadly
rounded; postero-lateral somewhat concave, the two meeting at an acute angle
in the middle of the side of the body; posterior margin straight.

Brarchial regions largely developed, tumid; a long transverse depression in
the carapace behind the gastric region; antero-lateral margin bordered by a
fringe of sete.

Third joint of external maxillipeds very small; second joint stout and large

First pair of legs short, with short carpus and flattened elongated manus
having a fringe of sete on its upper border.

Second and third pairs of legs sub-equal, longer than the first, slender,
ending in a sharp claw; the third pair slightly longer than the second.

Fourth pair immensely developed, exceeding in length the width of the
carapace, terminating in a stout claw.

Fifth pair shortest. reaching to about the middle of the third joint of the
fourth pair; usually held in an elevated position over the posterior portion of
the carapace.

Width of carapace a little less than 14 inch; length, 1¢ inch.

Total length from claw to claw at fourth p:ir, °4 inch.

Habitat, the sand-constructed tube of an annelid.

I found this curious little crustacean on the tube of an annelid common on
the sandy flats left bare at low tide in Tomales Bay. While digging for those
sand-excavating lobs'ers, the Gebie and CVallianasse, I found in abundance the
sandy tubes of an annelid about six inches long, with numerous joints or
nodes, each of which was surrounded by a circlet of set, by whose action
the creature propelled itself at pleasure up and down the tube.

Believing the worm to be a new species, I gathered some, and while pulling
the tube to pieces, and admiring the rich brownish red tint conspicuous at
each node cf my new prize, I was surprised to see a long narrow creature

2

move out, as I believed, head first; but a nearer inspection showed me that
the motion was sideways, and t!at the new-comer was no fourteen-legged
amphipod or isopod, but a true decapod crustacean.

The short chelee, extremely lengthened fourth pair of legs, and short, broad
body, are so many adaptations to the mode of life of this creature, which
finds an ample dwelling-place in the space intervening between the body of
the annelid and the inside of the tube; up and down which it moves with its
long fourth pair stretched ont in such a manner as to to give it the elongated
appearance of a Caprella.

The width of Tubicola longipes from end to end of the fourth pair of legs is
eight times greater than its length from front to back.

This is, so far as I am aware, the only instance known of a decapod crus-
tacean becoming the guest or commensal of an annelid, for although the
species of the family Pinnotheride are all commensals, most of them reside
between the folds of the mantle of large bivalve mollusks, such as mussels
or clams (thus the Fabia subquadrata lives within the mantle of Pachydesma
crassttelloides, a large clam of this Coast), and a few live within the tests of
Echini, close to the anal aperature.

It is most probable that this worm and its commensal may occur in many
other places besides ‘Yomales Bay, possibly in San I’rancisco Bay, and I should
be much obliged if some of our friends who may go out on a fishing excursion
would bring me specimens, in alcohol, of the worm and its tubes, that I may
find whether the crab is its constant companion in all localities.

The worm is one which is frequently used for bait.

On April 20th, the females of this interesting little crustacean was loaded
with spawn.

Phyllodurus abdominalis. Stimpson.

When Stimpson, in his Crustacean and Echinodermata of the Pacific Shore
of N. A., page 71, first de-cribed this species, the female only was known to
him. This female, like all those belonging to the family Bopyride is of com-
paratively large size, broad and clumsy in appearance, and lives attached to
another crustacean.

The crustacean frequented by this commensal is Geb‘a pugettensis, a marine
crayfish common on these shores.

About April 24th, I gathered a great number of Gebias in Tomales Bay, and
found that most of them, all except the largest specimens, had a female P.
abdominals attached to one of the abdominal pairs of feet, to which it clung
closely by means of its hooked claws.

A close inspection revealed, beside or near the large female, a small and
slender male, a kind of miniature edition of its stout mate.

Never more than a single pair were ever found attached to one Gebia, but
the males appeared so regularly to accompany the females, that I believe that
in the few cases I did not find them, it was because they had dropped off in
handling the specimens.

The males do not live attached to the Gebia, but are free to rove, and their
constant presence at this season by the side of the females proves that this
is their season of love.

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Male. Head semi-circular anteriorly, closely united to the succeeding seg-
ment. Third and fourth thoracic segments widest. Body oblong, boat-shaped,
tapering slowly from the fourth to the seventh thoracic segment.

Outer antennze four-jointed; inner very small, reaching about to the middle
of the second segment of the outer.

Eyes too small to be distinguished by a Coddington lens.

First abdominal segment a little narrower than last thoracic, but flat; suc-
ceeding segments tapering rapidly to the sixth or telson, which is pointed at
the end, and is provided on each side with a small lamella, giving the whole
telson somewhat the appearance of a spear-head.

The lateral laminz of the first five abdominal segments round in sections
instead of segmental, as in the female, and considerably longer than the width
of the segments to which they are attached.

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