FAMILY, I-SILUEID^. 501 



Genus, 30 — Exostoma, Blyih. 



CMmamahthys, Sauvage. 



Qill-opemngs narrow, the menibrcmes confiueni with the shm of a broad isthmus. Head depressed and covered 

 sivperiorly with soft shim. No thoraoic adhesive arppoA-atus. Mouth imferior, with the Ups reflected a/rownd the whole 

 or most of its cwcvmference, and usually covered with tubercles. Nostrils close together, sepa/rated by a ba/rbel. Hight 

 barbels. Teeth in theja/ws in several rows : palate edentulous. Anterior dorsal fin with a rudimentamj spine and six 

 ra/ys; adipose fin long and low. Pectorals vertical in their upper, horizontal in their lower half, the spine enclosed in 

 shin. Ventral with six rays inserted some Mstance behind the rayed dorsal, its form as in the pectoral. Caudal 

 sgua/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. — At present there are six 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 iu 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 afluents of 

 Ganges. 



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



4. Exostoma StoUczhce. 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. 



Olyptostermwm labiatus, McClell. C. J. N. H. ii, p. 680. 



Exostoma labiatum, Blyth, P. A. S. of B. 1860, p. 156 ; Giinther, Catal. v, p. 265 ; Day, Proc. Zool. See. 

 1869, p. 626. 



D- i/0, P. ttIt^, V. 6, A. i, C. 17. 



Length of head 1/6, of pectoral 1/6, of caudal 1/6, height of body 1/8 of the total length. Eyes — small, 

 situated in the posterior two-fifths of the head. Mouth small, inf erior^ transverse : jaws in the form of a double 



crescent or D2-shape. Lips broad, with a median and a lateral lobe on either side, 

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

 extend to the pectoral fin. Fins^m in the preceding species. Caudal slightly 

 forked. Golowrs — uniform. 



Habitat. — Mishmee Mountains, Bast .A^sam. 



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



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



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



Length of head 4f , of caudal 6|-, height of body 6 in the total length, ^i/es— small, situated on the 

 upper surface of the head, and the width of the interorbital space nearly equals the length of the snout, 

 which is broad and depressed. Mouth inferior and transverse, sulcus behind lower lip interrupted. GiU- 

 openings not continued on to the lower surface of the head. J5cw&eZs— the nasal about three tunes as long as 

 the orbit : a fleshy appendage to the maxilla having a rudimentary barbel : two pairs behmd the lower hp 

 arising on a transverse line. Teeth^none on the palate. Ifes— pectoral sub-horizontal, its rays plaited below : 

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

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

 almost lunated. ^?V.*esseZ— small, in two rounded lobes, both enclosed in a bony capsule. Golowrs— jellowish 

 brown. 



» The other two species alluded to are as follows:— , , , ,i i? .t. i *» ■Po/.f^^ai ,00^1,0= ^on+rs,! 



E. Damdi. The interspace between the two dorsal fins equals the length of the latter. Pectoral reaches ventral. 



Eastern Tibet. 



B. Ouder row of teeth compressed. 



E. AndersoTWi. Lower labial fold interrupted. Ehanio. 



