FAMILY, I-SILURID^. 501 



Genus, 30 — Exostoma, Blyth. 



Chimarriclithys, Sauvage. 



Gill-openings narrow, the membranes confluent with the shin of a broad isthmus. Head depressed and covered 

 superiorly with soft shin. No thoracic adhesive apparatus. Mouth inferior, with the lips reflected around the lohole 

 or most of its circumference, and usually covered with tubercles. Nostrils close together, separated by a barbel. M.ujlit 

 barbels. Teeth in the jaws in several rows : palate edentulous. Anterior dorsal fl.n ivith a ru,dimentary spine and su: 

 rays : adipose fin long and Imv. Pectorals vertical in their upper, horizontal in their lower half the spine enclosed m 

 shin. Ventral with six rays inseHed seine distance behind the rayed dorsal, its form as m the pectoral. Caudal 

 squa/re, emarginate or forhed. Air-vessel enclosed in bone. 



This peculiar mountain Genus has its lips adapted for a sucker, the chest likewise appears to form a flat 

 adhesive surface, bounded by the striated rays of the pectoral and ventral fins. 



Geographical distribution.— M, present there are sis species of this Genus known, four of which are 

 included in this work. These fishes extend from the upper waters of the Indus, along the Himalayas, the 

 Mishmee Mountains in East Assam, Tenasserim to Eastern Tibet on the confines of China. 



SYNOPSIS OP SPECIES.* 



A. Teeth in jaws pointed. 



1. Exostoma labiatum. Lower labial fold uninterrupted. The interspace between the first and adipose 

 dorsal fins equals equals 2/3 the length of the latter. Anal commences much nearer the base of the caudal than 

 that of the ventral. Mishmee Mountains. 



2. Exostoma Blythii. Lower labial fold interrupted. A short interspace between the dorsal fins 

 Anal commences in last 1/3 of the distance between ventral and base of caudal. Head waters or affluents of 

 Ganges. 



3. Exostoma Serdmorei. Snout more pointed. Caudal forked. Tenasserim. 



4. Exostoma Stoliczkv. Lower labial fold interrupted. Anal commences nearer the base of the ventral 

 than that of the caudal. Pectoral does not extend to the ventral. Upper waters of Indus. 



1. Exostoma labiatum. 



Glyptosternum labiatus, McClell. C. J. N. H. ii, p. 580. t> ry i e 



Exostoma labiatum, Blyth, P. A. S. of B. 1860, p. 15.5 ; Giinther, Catal. v, p. 2(35 ; Day, Proc. Zool. boc. 

 1869, p. 525. 



D. i/O, P. TT-T2) ^- 6, A. i, C. 17. 



Length of head' 1/5, of pectoral 1/5, of caudal 1/5, height of body 1/8 of the total length. %es— small, 

 situated in the posterior two-fifths of the head. Mouth small, inferior, transverse : jaws m the form ot a double 



crescent or oj-shape. Lips broad, with a median and a lateral lobe on either side, 

 havino' a barbel between. Nasal barbels reach the end of the snout : the maxillary 

 extend to the pectoral fin. Fins—a.a in the preceding species. Caudal shghtly 

 forked. Colours — uniform. 



Habitat. — Mishmee Mountains, East Assam. 



2. Exostoma Blythii, Plate CXVII, fig. 2. 

 Day, Proceedings Zoological Society of London, 1869, p. 525. 



D. i/0, P. ^, V. 6, A. 8 (f), C. 13. „ .. ,^ ,1, 



Lenf^h of head 4i, of caudal 6h height of body 5 in the total length. %e.s-small situated on the 

 upper sui-face of the head, and the width of the interorbital space nearly equals the length ot the snout, 

 which Ls broad and depressed. Mouth inferior and transverse, sulcus behind lower hp interrupted. Gill- 

 openings not continued on to the lower surface of the head. Barbels-the nasal about three tunes as long as 

 the orbit: a fleshy appendage to the maxiUa having a rudimentary barbel: two pairs be hmd the lower lip 

 arisino- on a transverse line. Teeth-none on the palate. K»s-pectoral sub-honzontal its rays plaited below : 

 base oi adipose more than twice as long as that of the rayed fin. Dorsal arising slightly m advance ot the 

 ventrals, its spine weak. Ventrals sub-horizontal. Caudal with its outer rays slightly produced, rendering it 

 almost lunated. Air^essel-smi^ll, in two rounded lobes, both enclosed in a bony capsule. CoJoww-yeUowish 

 brown. 



The other two species alluded to are as follows : — „,,. T>.ii..,fi 



KDavidi. The interspace hetweea the two doi-sal tins equals the length of the latter. Pectoral reaches ventral. 



B. Outer row of teeth CO 

 E. Andersonii. Lower labial fold interrupted. Ehamo. 



Eastern Tibet. ^ ^ ^^ ^, , 



B. Outer row of teeth compressed. 



