LIBRARY OF THE UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN 590.5 FI v.39 cop. 3 NATURAL HISTORV. SURVEY FIELDIANA: ZOOLOGY A continuation of the ZOOLOGICAL SERIES of FIELD MUSEUM OF NATURAL HISTORY VOLUME 39 NATURAL HISTORY SURVEY FEB 11 1971 MRP1RY FIELD MUSEUM OF NATURAL HISTORY CHICAGO, U.S.A. ■I •.39 10. 27 t«p.3 FIELDIANA • ZOOLOGY Published by CHICAGO NATURAL HISTORY MUSEUM Volume 39 February 27, 1959 No. 27 NEW SPECIES OF FRESH-WATER CATFISHES FROM NORTH BORNEO Robert F. Inger Curator, Division of Amphibians and Reptiles AND Chin Phui Kong Agriculture Department, Colony of North Borneo INTRODUCTION During the course of two zoological expeditions to North Borneo in 1950 and 1956, extensive collections of fresh-water fishes were made. Among them were the new forms described below. Most of the fishes were caught in the Kinabatangan River, the largest in North Borneo, or in its tributaries between Malapi (5° 30' N./1180 16' E.) and Kua- mut (5° 13' N./117° 30' E.). The two principal localities are Deram- akot (5° 17' N./117° 33' E.) and Lamag (5° 30' N./1170 50' E.). A few specimens were obtained in a tributary of the Kalabakan River, which empties into the sea at the extreme southeastern corner of North Borneo. Between 1950 and 1956 the junior author collected additional material from the Segama River, which lies immediately south of the Kinabatangan basin, and from the Labuk River north of Sandakan Harbour. Abbreviations used are CNHM (Chicago Natural History Museum) wk and SU (Natural History Museum, Stanford University). Wallago macula tus, new species Holotype. — Chicago Natural History Museum no. 68038. An adult Flught in the Kinabatangan River at Deramakot, Kinabatangan Dis- trict, North Borneo, on May 5, 1956, by Robert F. Inger and P. K. Chin. Diagnosis. — A Wallago with a row of large black blotches below the lateral line, with 56-64 branched anal rays, and with 13-15 bran- chiostegals. LiMafcy of Congress Catalog Card Number: 59-9^80 tfo. 867 279 j ! ~» l NATURAL HISTORY SURVEY fc , . LIBRARY Afl Tfi AQQ&, 280 FIELDIANA: ZOOLOGY, VOLUME 39 Description ofholotype. — Dorsal i,4; pectoral 1,14; ventral i,9; anal ii,64; branchiostegals 14; gill rakers 5 + 13; standard length 332 mm. Body compressed behind head; dorsal profile concave over eyes, rising to dorsal origin, then horizontal; ventral profile convex; head broad, 3.82, width 1.55 in length; body deepest before ventral inser- tion, 4.88; snout broadly rounded in outline, flat above, four times eye diameter; nostrils one eye diameter apart, the anterior about same distance from mouth; eye 10.73 in head, 5.5 in interorbital; lower jaw extending beyond upper; maxilla ending below center of eye; both jaws with six or seven irregular rows of depressible, conical teeth, those of inner rows the longest; vomerine teeth in separated oval patches; maxillary barbel ending at level of third or fourth anal ray; mandibular barbel not reaching edge of gill membrane, shorter than ventral fin; gill rakers very stiff, some forked, less than one-fourth length of gill filaments. Dorsal origin above last third of pectoral, fin shorter than pec- toral and slightly longer than postorbital part of head, all rays flex- ible; pectoral inserted low on side, osseous portion of first ray about 2.5 in head, second and third branched rays longest; pectorals over- lapping ventrals; ventrals moderately short, about three-fifths length of dorsal, overlapping origin of anal; anal base 1.6 in standard length; anal narrowly separated from caudal; caudal damaged, deep- ly forked in paratypes. Color (shortly after death) olive above, silvery below, with a row of bold dark blotches below lateral line. In alcohol slate above, lighter below, with blotches conspicuous; fins with a very light dust- ing of melanophores on membranes; dorsal membrane darker; a small black spot at base of caudal. Measurements (in millimeters) : Total length 365; standard length 332; head length 86.9, width 56.1; body depth 68.0; snout 33.9; eye 8.1; interorbital 44.6; anal base 205. Paratypes.— Eleven (CNHM 68033-36) from tributaries flowing into the Kinabatangan at Deramakot; 3 (CNHM 44843, 68037) from the Kinabatangan River at Lamag. Standard length varies from 86.8 to 320 mm. The maxillary barbel is relatively longer in smaller fishes, overlapping the anterior third of the anal at a maximum. The black blotches have faded in the largest paratype, but were as conspicuous as in all the others when the fish was fresh. Gill raker counts are 3-5+10-14, total 13-19; they vary with standard length as shown in Table 1. j HS •i r ,2.7 * INGER AND CHIN: FRESH-WATER CATFISHES 281 Table 1. — Variation in Gill Rakers on the First Arch in Wallago maculatus Standard length . . 87 87 106 109 114 119 121 125 140 158 163 173 320 332 Rakers, lower limb . 10 11 11 10 11 13 13 12 13 14 12 13 13 13 Rakers (total) 13 15 14 14 15 16 17 16 18 19 16 18 17 18 In the smaller fishes the cores of developing rakers can be seen in the body of the gill arch. The number of unbranched anal rays also varies with size, the two smallest fishes having four such rays and the two largest only two. The total number of rays, however, is independent of standard length. Counts for the entire series including the holotype are: ii-iv, 56-64, total rays 60-66, mean total 63.2±0.5, N=13. Other counts and proportions are as follows, again including the holotype: pectoral 1,13-15 (mean 1,14.1 ±0.2; N=12); ventral i,7-9 (mean 8.6±0.2; N=13); branchiostegals 13-15 (mean 13.6±0.2; N=14); head 3.74-4.01 (mean 3.89±0.03; N=12); depth 4.50-5.90 (mean5.17±0.13;N=10). Comparisons. — This species is the only known member of the genus that has a row of large black spots low on the sides. Its colora- tion further differs from that of miostoma in having pale dusky in- stead of black fins. The total anal ray counts (60-66, mean 63) are lower than those of other species, miostoma having 64-72, leeri 67-73, tweediei 70-74, and attu 86-93. The branchiostegals (13-15, mean 13.6) are also fewer in number, miostoma having 15-16, leeri 16-17, tweediei about 15 and attu 18-20. Information on attu, miostoma, and leeri is from Weber and de Beaufort (1913), that for tweediei from Hora and Misra (in Hora and Gupta, 1941). Wallago maculatus appears to have more gill rakers than miostoma or leeri, but the comparison is complicated by the association between standard length and number of rakers. Weber and de Beaufort give 9 as the count for the lower limb of the first arch, and, though the sizes of the fishes from which these counts came are unknown, these counts are lower than those of maculatus (see Table 1). A 308 mm. miostoma from Singapore (SU 14839) has 5 + 11 rakers and a 248 mm. leeri from Sumatra (CNHM 15744) has 4+11. Thus both of these have smaller counts than correspondingly large maculatus. The holotype of tweediei has 3 + 12 rakers (Hora and Misra, op. cit.), and since it is from three to four times the size of the largest maculatus it probably has fewer gill rakers than the latter at all sizes. Wallago attu has 21 rakers on the lower limb of the arch (Weber and de Beau- fort, 1913). 282 FIELDIANA: ZOOLOGY, VOLUME 39 Ompok sabanus,1 new species Holotype. — Chicago Natural History Museum no. 44828. Adult female with enlarged ova from the Segama River at the Segama Estate near Lahad Datu, Lahad Datu District, East Coast Residency, North Borneo. Collected May 30, 1950, by P. K. Chin. Diagnosis. — An Ompok with 50-65 anal rays, with mandibular barbel overlapping anterior half of anal, and with maxillary barbel somewhat longer. Description of holotype. — Dorsal 4; pectoral 1,12; ventral i,6; anal ii,54; branchiostegals 10; gill rakers 3+13; standard length 134 mm. Head 5.40, slightly depressed over snout; body compressed, dorsal profile slightly convex, rostral-dorsal profile almost straight, a weak concavity behind eyes; ventral profile convex anteriorly; body deepest at anal origin, 3.87; snout short, subequal to eye; nostrils separated by half an eye diameter, anterior one at tip of snout, both mesad from root of maxillary barbel; eye covered by skin, 4.90 in head, 2.60 in interorbital ; interorbital 1.90 in head; maxilla ending before orbit and at level of orbital center; teeth pointed, in bands, two to four rows in upper jaw, four rows in lower, vomerine teeth in a single transversely elongate band, constricted at center; maxillary barbel overlapping half of anal; mandibular barbel ending 10 mm. anteriorly. Dorsal origin just anterior to anal origin, distance from tip of snout 3.2 in standard length, 2.3 in distance to base of caudal; first dorsal ray longer than head minus snout; pectoral inserted low on side, longer than head, stiff portion of spine subequal to head minus snout; ventral small, slightly longer than eye diameter; anal base 1.53 in standard length; a distinct gap between anal and caudal; caudal deeply forked, the lobes pointed. Color (in alcohol) pale brown, somewhat darker along back; dark humeral spot; a thin mid-lateral black line, ending at caudal base in a diffuse round dark spot; fins hyaline. Measurements (in millimeters): Total length 167.5; standard length 134.0; head length 24.5; body depth 34.5; eye 5.0; interorbital 13.0; predorsal 41.5; anal base 87.0. Paraty pes. —Eleven (CNHM 44829) from the type locality; 99 (CNHM 44830-35, 68024-29, 68031) from the Kinabatangan basin between Malapi and Kuamut; one (CNHM 68030) from a tributary of the Kalabakan River, Tawau District. 1 Sabah is an old name for North Borneo. INGER AND CHIN: FRESH-WATER CATFISHES 283 The mandibular barbel may overlap as little as one half or as much as three fourths of the anal. The maxillary barbel is always a few millimeters longer, but it does not reach the caudal. Variation in counts and body proportions is as follows (including holotype) : pectoral 1,11-13 (mean I,12.5±0.1; N= 13); anal ii,53-64 (mean ii,58.3±0.3; N=44); branchiostegals 9-12 (mean 10.5±0.1; N=32); gill rakers 3-5 + 10-17, total 13-22 (mean total 17.1±0.3; N=29); standard length 68.8-132 mm.; head 4.23-5.73 (mean 5.18± 0.06; N=24); depth 3.91-4.73 (mean 4.18±0.05; N=20). Males over 100 mm. long have 8-14 (mean 10.9±0.4; N=16) retrorse hooks on the inside of the pectoral spine. Remarks.— This catfish is one of the most abundant fishes in the flat portion of the basin of the Kinabatangan River. At Deramakot the fishermen using cast nets caught more Ompok sabanus in the river than any other species and 24 of the paratypes were obtained this way. An additional 22 were caught in the river by means of seines, and 19 others were collected in the mouth of a small, muddy trib- utary. Significantly, not one was collected in the clear, rock-bottom streams in the Deramakot area, although the single individual from the Kalabakan basin came from a clear-water creek. Comparisons. — This form is similar to eugeniatus Vaillant (type locality Kapuas River, southwestern Borneo) from which it differs in pectoral ray and branchiostegal counts and in barbel lengths. The late Dr. L. Bertin (Museum National, Paris) examined the type and paratype of eugeniatus and informed us that the pectoral counts of both are 1,11. Although the range of pectoral counts in sabanus is 1,11-13, only one of the 43 counted has 11 rays. A similar overlap occurs in branchiostegal counts, which Dr. Bertin determined as 9 and 9/10 in eugeniatus. Only two specimens of sabanus have as few as 9, the others ranging up to 12. The counts given for eugeniatus of Sumatra by Weber and de Beaufort (1913) agree with those of the type and paratype in both characters. The lower branch of the first gill arch in Sumatran eugeniatus has 12 rakers (Weber and de Beaufort, 1913). One paratype of sabanus has 10 and two others have 12. The other 27 sabanus counted have from 13 to 17 on the lower limb. Although individual variation is shown by the barbels, their rela- tive lengths also distinguish these two forms. All known specimens of eugeniatus have mandibular barbels exceeding the length of the maxillary and reaching beyond the caudal base. The maxillary is the 284 FIELDIANA: ZOOLOGY, VOLUME 39 longer barbel in sabanus and in no specimen does it reach the end of the anal. Ompok sabanus and 0. eugeniatus are the only Indo-Australian Ompok in which the mandibular barbel extends beyond the tip of the pectoral. The first further differs from borneensis and leiacanthus in having the anal separated from the caudal, from weberi in having more anal rays (55-66 as opposed to less than 50 in weberi), from hypophthalmus in having fewer anal rays (more than 75 in hypoph- thalmus), and from bimaculatus in having more gill rakers on the lower limb of the first arch (10-17 as opposed to 9 in bimaculatus). Kryptopterus parvanalis, new species. Figure 46. Holotype. — Chicago Natural History Museum no. 68014. Adult from Kinabatangan River at Deramakot, Kinabatangan District, North Borneo, collected May 6, 1956, by Robert F. Inger and P. K. Chin. Diagnosis. — A Kryptopterus totally lacking a dorsal fin, with max- illary barbel usually reaching the end of the preopercle or slightly beyond, and with mandibular barbel shorter than eye diameter. Description of holotype. — Dorsal absent; pectoral 1,14; ventral i,7; anal 75; caudal i,15,i; branchiostegals 14; gill rakers 7+19; standard length 201 mm. Body compressed; dorsal profile straight, with concavity over head; ventral profile convex; head 4.71, flattened above; body deepest at ventral insertion, 4.43; snout broadly rounded, about twice eye diam- eter; nostrils separated by two-thirds of eye diameter, anterior pair near tip of snout; eye covered by skin, 5.78 in head, 2.45 in inter- orbital; interorbital 2.36 in head; lower jaw extending beyond upper, maxilla ending before orbit and opposite its lower third; teeth pointed, depressible, in bands of four or five rows in each jaw; pointed vomer- ine teeth in a V-shaped double row; maxillary barbel reaching end of preopercle; mandibular barbel about one half of eye diameter; gill rakers subequal to filaments, about half eye diameter. Pectoral inserted in lower half of side, slightly longer than head minus snout, stiff portion of spine less than head minus snout; pec- toral overlapping ventral ; ventral short, less than twice eye diameter, not reaching anal; anal base 1.7 in standard length; anal narrowly separated from caudal; caudal deeply forked, lobes pointed. Color (in alcohol) pale brown, much darker along mid-dorsal area; a dark humeral spot; fins hyaline. 3. ■a =3 I CQ S "i- f 285 286 FIELDIANA: ZOOLOGY, VOLUME 39 Measurements (in millimeters): Standard length 201; head length 42.7; body depth 45.4; snout 15.1; eye 7.4; interorbital 18.1; anal base 120; pectoral 33.9. Par aty pes. —Sixteen (CNHM 68015-22) from the type locality; 8 (CNHM 44840-42) from the Kinabatangan River between Lamag and Bilit; 3 (CNHM 44837-38) from the Segama River at Lahad Datu; 1 (CNHM 44839) from the Labuk River. Standard length varies from 57.2 to 244 mm. The maxillary barbel in three does not reach the end of the preopercle; in all others it ex- tends to the end of the preopercle or between the latter and the opercle. The mandibular barbel is minute in all. Variation in counts and pro- portions (including the holotype) is as follows: Pectoral 1,13-15 (mean I,13.9±0.2; N=19); anal 71-83 (mean 76.1±0.6; N=22); ventral i,6-8 (mean i,7.2±0.1; N=18); branchi- ostegals 13-16 (mean 14.1 ±0.2; N= 18); gill rakers 4-7+17-21, total 22-27 (mean 24.3±0.3; N=20); head 4.19^.92 (mean 4.62±0.04; N= 18); snout in head 2.64-3.22 (mean 2.88±0.04; N=13); depth 4.19- 5.02 (mean 4.62±0.06; N=16). The relative eye size decreases with increase in standard length; thus the eye-in-head ratio is 4.98 in a 101 mm. specimen and 6.48 in one 244 mm. long. The interorbital width has a more or less constant relation to head length, the interorbital ratio varying from 2.10 to 2.45, in paratypes 101 to 244 mm. Comparisons. — This form differs from other Kryptopterus lacking dorsal fins in the smaller anal count, number of gill rakers, and relative sizes of the barbels. It is most similar to apogon Bleeker. However, apogon has 78 to 91 anal rays (parvanalis 71-83), 15 to 17 branchiostegals (parvanalis 13-16, mean 14.1), 5+12-14 gill rakers (parvanalis 4-7+17-21), and maxillary barbels that do not extend beyond the orbit (usually to end of preopercle in parvanalis) . Data for apogon are from Bleeker (1851, 1862) with the exception of the gill raker count. The latter was supplied by Dr. M. Boeseman, Rijks-museum, Leiden. The Leiden museum has in its collections eight apogon placed in one jar by Bleeker. These range in length, according to Dr. Boese- man's measurements, between 119 and 350 mm. Bleeker's (1851) measurements of the four types were 118-175 mm. Bleeker later received additional specimens from the type locality (Bandjermassin, Borneo), from other places in southern and southwestern Borneo, and from Sumatra. In the Atlas Ichthyologique (1862, 2: 92) Bleeker listed twelve specimens (as micropogon= apogon) with a size INGER AND CHIN: FRESH-WATER CATFISHES 287 range of 118-320 mm. As the minimum size remained 118, it is highly probable that the smallest specimen measured by Dr. Boeseman (119 mm.) is one of the types. Gill raker count in that specimen is 5+13. The eight apogon examined by Dr. Boeseman fall into two sharply marked groups on the basis of gill raker count and size. The smaller group of five, 119-160 mm. total length (standard length 100-137), has 5 + 12-14 gill rakers. The larger group of three, 260-350 mm. total length (227-300 mm. standard length), has 5-6+20-22 gill rakers. Apparently micropogon (= apogon) of the Atlas is a composite spe- cies. Assuming that the smallest specimen (119 mm.) is actually the smallest member (118 mm.) of Bleeker's type series, apogon (or micro- pogon) has gill raker counts of 5 + 12-14. The identity of the larger specimens remains problematical. The difference in counts of the two size groups is probably not size-dependent, if one can argue by analogy from parvanalis, for the latter spans the two size groups without a corresponding dichotomy in gill raker counts. Kryptopterus micronema Bleeker has 86 to 93 anal rays, 14 gill rakers, and a maxillary barbel that does not extend beyond the orbit (Weber and de Beaufort, 1913) . Kryptopterus hexapterus Bleeker has more pectoral rays (1,16-17), a smaller head (at least 6.5 times in length), and longer barbels (both pairs reaching end of head) than parvanalis. Pangasius tubbi,1 new species. Figure 47. Holotype. — Chicago Natural History Museum no. 68047, from the confluence of the Deramakot River with the Kinabatangan River, Kinabatangan District, North Borneo. Collected May 6, 1956, by Robert F. Inger and P. K. Chin. Diagnosis. — A Pangasius with teeth in distinct, elongate vomerine and palatal groups, the two meeting at a point or narrowly separated and forming an oblique angle or arc; maxillary barbel usually reach- ing base of pectoral; eye large, four to five times in head; anal with about forty rays. Description of holotype. — Dorsal 11,7; pectoral 1,12; ventral i,5; anal iv,35; branchiostegals 8; gill rakers 5 + 12; standard length 228 mm. Dorsal profile horizontal behind dorsal, sloping downward in straight line before dorsal ; ventral profile convex, deepest at insertion of ventrals; depth 4.18; head 4.76, subcorneal; snout blunt; mouth 1 Named for Mr. J. A. Tubb, formerly Director of Fisheries, Colony of North Borneo. 288 FIELDIANA: ZOOLOGY, VOLUME 39 subterminal; anterior nostril its diameter distant from mouth; nos- trils separated by slightly more than diameter of anterior one; poste- rior nostril above line between anterior nostril and top of orbit; eye large, lower portion cut by horizontal from corner of mouth, 4.94 in head, 3.30 in interorbital ; interorbital evenly convex, 1.50 in head, maxillary barbel reaching end of opercle; mandibular barbel reaching below pupil; teeth in jaws small, in bands of three to five rows; vomer- ine teeth in two transversely elliptical groups narrowly separated, major axis of each group about twice the minor; palatal teeth in sim- ilar patches, each group narrowly separated from the vomerine tooth patch; palato- vomerine teeth forming a broad, evenly curved arc. Dorsal origin above posterior half of pectoral, snout-dorsal dis- tance 2.92 in standard length; dorsal spine moderately strong, with low serrations posteriorly, tip broken (1.75 in head of a 147 mm. paratype) ; adpressed dorsal not reaching level of anal origin; adipose inserted over last third of anal, base half its height and less than half of eye; pectoral inserted just above horizontal from corner of mouth, pointed ; pectoral spine moderately strong, finely serrated posteriorly, subequal to head; ventrals subequal to postorbital part of head, reach- ing anal origin; anal origin slightly behind center of standard length, its base 3.29 in standard length; margin of anal slightly concave; tips of caudal lobes missing, fin deeply forked in paratype. Color (in alcohol) grayish, without distinct markings; much lighter on belly; dorsal and caudal faintly dusky; other fins pigmentless. Measurements (in millimeters) : Standard length 228, head 47.9, depth 54.5, snout 17.6, eye 9.7, interorbital 32.0, anal base 69.4, pec- toral spine 44.3. Paratypes. — Seven (CNHM 68044^46) from the type locality; one (CNHM 68048) from the Kinabatangan River, ten miles upstream from Deramakot, Kinabatangan District; six (CNHM 44856-59) from the Kinabatangan River near Lamag; seven (CNHM 44860) from the Segama River, near Lahad Datu. The palatal tooth patches contact the vomerine groups at a point in several specimens. Barbel length varies slightly, the maxillary reaching between the end of the opercle and the base of the pectoral, and the mandibular extending to a vertical from the pupil or from the posterior rim of the orbit. Variation in body proportions and meristic characters in all speci- mens is as follows: dorsal 11,7-8 (8 in one); pectoral 1,11-12 (mean I,11.7±0.1; N=19); ventral i,5; anal iv-vi, 33-38, total rays 38^3 289 290 FIELDIANA: ZOOLOGY, VOLUME 39 (mean 39.7±0.3; N=20); branchiostegals 7-10 (mean 8.5±0.2 N=19); gill rakers 3-5+8-12, total 11-17 (mean 14.0±0.4; N=19) standard length 64.5-228 mm.; head 3.91-5.04 (mean 4.39±0.06 N=21); depth 3.97^.94 (mean 4.39±0.07; N=14); eye 3.91-4.97, ratio increasing with standard length; anal base in standard length 2.99-3.50 (mean 3.30±0.04; N=15). Remarks. — The holotype was caught in a trammel net. One para- type (68048) was collected with a seine over a gravel bar and seven (68044^46) with a cast net, all in the Kinabatangan River. Comparisons. — The high anal count distinguishes P. tubbi from all of its Indo-Malayan congeners except polyuranodon Bleeker (type locality Bandjermassin, Borneo), pleurotaenius Sauvage (type local- ity Thailand), fowleri Smith (type locality Thailand), and longibarbis Fowler (type locality Thailand). P. pleurotaenius is distinguished by its lateral black band. The long maxillary barbel of longibarbis, reach- ing the anal, differentiates it from tubbi. The maxillary barbel of fowleri is smaller than that of tubbi; these two forms are further differ- entiated by the arrangement of the palatal tooth patches, which are perpendicular to the vomerine groups in fowleri and oblique in tubbi. The vomerine teeth of polyuranodon, in a single large quadrate group of which the two axes are subequal, separate it from tubbi. These two species also differ in depth (polyuranodon 5.0-5.3) and head (polyuranodon 5.2-5.5). In addition to the high anal count, tubbi differs from other Bor- nean Pangasius in the following characters : arrangement and propor- tions of palatovomerine teeth (nasutus Bleeker, nieuwenhuisi Popta, and pangasius Hamilton), length of barbels (macronema Bleeker, micronema Bleeker, and dezwanni Weber and de Beaufort), and vari- ous body proportions. Leiocassis robustus, new species. Figure 48. Holotype. — Chicago Natural History Museum no. 68001, from the Kinabatangan River at Deramakot, Kinabatangan District, North Borneo. Collected by Robert F. Inger and P. K. Chin on May 12, 1956. Diagnosis. — A Leiocassis with head covered by smooth skin ; head wide, interorbital longer than snout; pectoral spine more than half head length; maxillary barbel reaching pectoral; adipose distinctly longer than its distance from dorsal; no bands or spots on sides. Description of holotype. — Dorsal 11,7; pectoral 1,9; ventral i,5; anal v,10; caudal i,15,i; gill rakers 7+13; total length 275 mm.; standard length 223 mm. INGER AND CHIN: FRESH-WATER CATFISHES 291 Robust; dorsal and ventral profiles about equally convex; depth at dorsal origin 3.42; head subcorneal, length 3.84, breadth 1.12 in length, depth 1.36 in length; skin of head smooth, no exposed bones posteriorly; occipital process parallel-sided, 8.2 mm. wide at base, 21.8 mm. long, end bifurcated around tip of basal process of dorsal fin; snout blunt, slightly damaged at tip; eye in anterior half of head, small, 8.9 in head length, 4.0 in interorbital ; interorbital larger than snout, 2.2 in head; vomerine teeth in a crescentic band, thickest in center; nasal barbel ending somewhat more than one eye diameter behind eye; maxillary barbel reaching base of pectoral; outer mental barbel extending just beyond edge of gill membrane directly behind it; inner mental barbel about half as long as outer. Dorsal origin much closer to tip of snout than to caudal flexure; spine stout, without teeth, 1.2 in head, osseous portion shorter than first soft ray; dorsal base 1.46 in adipose base; adipose 5.25 in stand- ard length; dorsal-adipose distance 1.33 in adipose; pectoral inserted low on side; spine stout, 1.2 in head, posterior border with 26 strong serrae; tip of pectoral below last rays of dorsal; humeral process bluntly pointed, its post-opercular length once and a half its width and longer than snout; ventral insertion below mid-point of dorsal- adipose gap, separated from anal by an eye diameter; anal origin behind origin of adipose, end opposite that of adipose; anal base 1.33 in adipose; caudal deeply forked, both tips with a short filament; caudal peduncle about 1.5 times its least depth. Color (in life) dark reddish brown, lighter below; no dark spots or bands; in alcohol uniform slate gray, lighter below; fins dusky. Measurements (in millimeters): Total length 275; standard length 223; head length 58.2; head width 51.7; head depth 42.9; interorbital 26.4; eye 6.6; dorsal base 29.2; adipose base 42.5; dorsal-adipose 32.0; dorsal spine 47.2; pectoral spine 47.2. Paratypes.— CNHM 68002-3 (5) from the type locality; CNHM 44827 from Lamag, Kinabatangan District, North Borneo. These agree with the holotype in all characters mentioned in the diagnosis. In all specimens the parallel-sided occipital process meets the basal process of the dorsal fin. The variation in counts and pro- portions given below includes the holotype. Dorsal 11,7; pectoral 1,8-9 (one with 8); ventral i,5; anal v-vi,10- 11 (mean branched rays 10.6±0.2); gill rakers 5-8+12-15, total 19-22 (mean total 20.2±0.5); standard length 103.5-227 mm.; dorsal spine in head length 1.12-1.56 (mean 1.25±0.06); pectoral spine in head length 1.19-1.32 (mean 1.24±0.02). X 292 INGER AND CHIN: FRESH-WATER CATFISHES 293 Certain characters change with age so that mere ranges and aver- ages are relatively meaningless. The data (Table 2) show that as size increases there is also an increase in the number of serrae on the pec- toral spine, a relative reduction in head length, a relative widening of the head (shown both by overall head width and by interorbital width), a relative increase in body depth, and a relative increase in the length of the adipose fin. Remarks. — This catfish has been collected so far only in the muddy water of the Kinabatangan River, despite intensive fishing in small, clear tributaries. Six of the seven specimens were caught on hook- and-line baited with earthworms and while the Kinabatangan was in flood. The local people insist that this species can be caught only at high water. No information is available for the seventh fish except that it came from the Kinabatangan River. Comparisons. — The deep body and wide head distinguish robustus from all Indo-Malayan Leiocassis having the head covered with smooth skin. It also differs from all except fuscus Popta and mahakamensis Vaillant in the absence of contrasting light and dark spots or bands laterally. The dorsal spines of both fuscus and mahakamensis are less than half the head length and therefore much shorter than the spine in robustus. The distance between dorsal and adipose is longer than the base of the adipose in fuscus, mahakamensis, and stenomus but much shorter in robustus. In addition to the distinctions in body proportions, robustus differs from poecilopterus, micropogon, and host in the number of serrae on the pectoral spine. Table 2 indicates a correlation between standard length and the number of pectoral serrae in robustus so that the inter- specific differences in this character might be questioned. However, the four Leiocassis poecilopterus at hand have standard lengths of 141-158 mm. yet have fewer serrae (15-18) than smaller or larger robustus. The five micropogon available vary from 49 to 97 mm. and all have either 10 or 11 serrae; the largest micropogon is roughly the same size as the smallest robustus (103.5 mm.) yet has 7 fewer serrae (11 vs. 18). Both micropogon and poecilopterus have fewer gill rakers (totals 11-13 and 12-15, respectively) than robustus (19-22). The maxillary barbel, which reaches the base of the pectoral in robustus, is much shorter in micropogon, saravacensis, baramensis, merabensis, and hosi, not extending behind the center of the head in the five last. 294 FIELDIANA: ZOOLOGY, VOLUME 39 Table 2. — Ontogenetic Changes in Certain Counts and Body Proportions of Leiocassis robustus Standard length (mm.) 103.5 135 175 178 205 223 227 Standard length /head length.... 3.69 3.64 3.76 3.72 3.76 3.98 3.91 Standard length/body depth 4.03 3.66 3.82 3.70 3.42 3.42 3.00 Standard length /adipose length . . 5.38 5.00 4.29 4.46 4.31 5.26 4.00 Head length/width 1.24 1.21 1.22 1.20 1.15 1.12 1.07 Head length/interorbital 2.59 2.36 2.40 2.25 2.20 2.21 2.09 Pectoral spine serrae 18 20 23 22 24 26 26 Mystus sabanus, new species Holotype. — Chicago Natural History Museum no. 68088 from the Kinabatangan River at Deramakot, Kinabatangan District, North Borneo. Collected April 7, 1956, by Robert F. Inger and P. K. Chin. Diagnosis. — A Mystus with adipose fin several times length of anal base; median fontanel reaching base of occipital process; nasal barbel not extending beyond end of preopercle; eye five or more in head length. Description of holotype. — Dorsal 11,7; pectoral 1,10; ventral i,5; anal v,8; caudal i,15,i; gill rakers 6+16; branchiostegals 11; total length 165 mm.; standard length 120 mm. Dorsal profile rising evenly and rather steeply from tip of snout to origin of dorsal, thence sloping evenly to narrow part of caudal peduncle; ventral profile almost horizontal to anal origin, rising to waist of peduncle; depth 5.24; head moderately broad, scarcely taper- ing to tip of snout, length 3.64, smooth; fontanel ending at base of occipital process; anterior nostril tubular, near mouth opening; poste- rior nostril separated from anterior by half an eye length; eye centered between tip of snout and end of preopercle, 5.89 in head, 21.43 in standard length; maxillary tooth band curved, its width about 6 in its length, length of band 2.89 in head, 10.53 in standard length; maxillary barbel reaching caudal, nasal barbel reaching end of pre- opercle, outer mental barbel almost to ventrals, inner mental barbel beyond gill membrane. Origin of dorsal two-fifths of distance from snout to caudal flex- ure; spine moderate, weakly serrated behind, half of head length; margin of dorsal straight, base 1.88 in adipose; adipose half height of dorsal, base 3.19 in standard length; dorsal-adipose distance about one-fourth dorsal base; pectoral low on side; spine stout, weakly ser- rated behind, subequal to dorsal spine; margin of pectoral straight; ventrals inserted below end of dorsal, not reaching anal, margin weakly convex; anal origin approximately below center of adipose, anal base INGER AND CHIN: FRESH-WATER CATFISHES 295 2.98 in base of adipose; caudal deeply forked, upper lobe with a long filament. Color (in alcohol) pale yellowish brown, lighter below; a dark humeral spot; membranes of dorsal, anal, and caudal dusky; other fins colorless. Measurements (in millimeters): Standard length 120; head 33.0; depth 22.9; eye 5.6; dorsal base 20.0; adipose base 37.6; dorsal-adipose 5.1; anal base 12.6. Paratypes.— CNHM 68061 (1), 68085-87 (6) from the type local- ity; CNHM 68062 (5), 68089 (3) from the Kinabatangan River ten miles upstream from Deramakot; CNHM 44851 from Segama River at Lahad Datu, Lahad Datu District, North Borneo. The maxillary barbels of several do not quite reach the base of the caudal. The nasal barbels reach the end of the preopercle in about four-fifths of the paratypes and between the eye and the end of the preopercle in the remainder. The following counts and body proportions include those of the holotype. Dorsal 11,7; pectoral 1,9-10 (1,9 in one) ; ventral i,5; anal iv-v,8-9 (mean of branched rays 8.4±0.2; N=10); gill rakers 5-6 + 14-16, total 19-22 (mean total 20.5 ±0.3; N=10); branchiostegals 9-13 (mean 10.7±0.2; N=10); standard length 40.1-152 mm.; head 3.22-3.85 (mean 3.62±0.06; N= 9); depth 4.24-5.88 (mean 4.97±0.18; N=8); eye 4.97-6.57 in head, 17.22-23.93 in standard length; maxillary tooth band 2.70-3.05 in head, 9.50-11.07 in standard length; adipose base 2.80-3.25; anal base 2.45-3.58 in adipose. Comparisons. — The lengths of the adipose fin and the barbels dis- tinguish sabanus from all Mystus of southeastern Asia except nigri- ceps, cavasius, baramensis, and micracanthus. The last has only a very short fontanel widely separated from the occipital process and is thus sharply distinct from sabanus. Furthermore, micracanthus has a precaudal spot not found in sabanus. The adipose fin is shorter in baramensis than in sabanus, its distance from the dorsal equaling one third to one half the dorsal base in baramensis but at most one fourth (and usually much less) the dorsal in sabanus. The barbels of baramensis are also shorter than those of sabanus, the nasal, for example, rarely reaching beyond the eye in the former but usually to the end of the preopercle in sabanus. Both Mystus nigriceps and M . cavasius have larger eyes, narrower heads, and longer adipose fins than sabanus. Limiting comparison to fishes in the size range 55-135 mm., the head ratios for four Indian 296 FIELDIANA: ZOOLOGY, VOLUME 39 cavasius, four from Thailand, two from Sumatra (nigriceps or cavasius) , and seven sabanus are, respectively: 4.13-4.45, 4.01-4.47, 3.80-4.56, and 3.22-3.85. Eye in standard length ratios for the same fishes, re- spectively, are: 13.71-15.31, 14.67-17.60, 12.93-14.76, and 17.22-23.93. The ratios of standard length to length of maxillary tooth bands are, respectively: 12.00-15.69, 17.60-19.72, 16.73-18.42, and 9.50-11.07. The adipose fins in standard length ratios are 2.17-2.26 in two from Thailand, 2.26 in one from Sumatra, and 2.80-3.25 in sabanus. Fur- thermore, young cavasius (or nigriceps) from Thailand have distinct lateral stripes, which are not found in sabanus of the same size. Information on three Indian, two Thailand, and one Sumatran fish was kindly provided by Dr. E. Trewavas and Mrs. A. Martin of the British Museum. REFERENCES Bleeker, Pieter 1851. Derde bijdrage tot de kennis der ichthyologische fauna van Borneo. Nat. Tijd. Ned.-Indie, 2: 57-70. 1862. Atlas ichthyologique des Indes Orientates Neerlandaises. 2, 112 pp., pis. 49-101. Amsterdam, F. Muller. Hora, S. L., and Gupta, J. C. 1941. Notes on Malayan fishes in the collection of the Raffles Museum, Singa- pore. Part 1. Bull. Raffles Mus., no. 17, pp. 12-43, pis. 2-4, 9 text figs. Weber, Max, and de Beaufort, L. F. 1913. The fishes of the I ndo- Australian Archipelago. 2, xx + 404 pp., 151 figs. Leiden, E. J. Brill, Ltd.