NATURAL SCIENCES OF PHILADELPHIA. 283 



COEYDOEAS SPLENDENS, Cast. 



CalUcTitTiys splendens^ Casteluau, Anim. Nouv. Rar. Am. Sud. 39, Tab. 18, 

 f. 3. 



Rio Tocantins. 



OTOCINCLUS, Cope. 



Proc. Acad. Nat. Sci., Phila., 1871, p. 112. 



Subfamily Hypostomatina of Giintlier's system. Ventral fins 

 immediately below the front of the short dorsal ; branchial fis- 

 sures extending a little below pectoral fins. Vent a little behind 

 the middle of the body. Body shielded with several series of 

 plates, the anterior less numerous. Thoracic and abdominal re- 

 gions with numerous shields. No adipose fin ; dorsal with weak, 

 pectoral with strong spine. Inter-operculum horizontal, beneath 

 the orbit, unarmed. No barbels. The teeth as in allied genera. 

 Post-temporal region pierced with numerous foramina, forming a 

 sieve, which only separates the water from a large cavit}^ on each 

 side of the modified anterior vertebrae, by the thin skin which 

 covers it. 



This genus is allied to Hypoptopoma, and apparently to Rhine- 

 lepis. The arrangement of the opercular bones is like that seen 

 in the former (see figure of H. hilohatum in Proc. Am. Phil. Soc, 

 1870, p. 561), while the absence of adipose fin and general rugo- 

 sit}'' are seen in the latter. Neither exhibits the remarkable per- 

 foration of the post-temporal plate. This is, in the only known 

 species, so extensive as to cover the whole plate to the orbit, which 

 becomes thus a skeleton sieve of some beauty, through which the 

 cavity within may be plaiuly seen. Its use is unknown, but maj'' 

 be connected with the function of hearing, as the genus has no 

 swim-bladder. 



OTOCINCLUS VESTITTIS, Cope, sp. nov. 



Body compressed, head elongate oval, neither elevated. Muz- 

 zle rounded-acuminate, projecting much beyond mouth, nareal 

 opening near orbit. Loreal region vertical, a canthus rostralis ; 

 muzzle a little convex between nares and orbits ; profile gentl}' 

 arched from dorsal fin to end of muzzle. Scales obtusely angu- 

 late behind, the exposed surface covered with distant elongate 

 prickles. Four rows on the caudal peduncle, the third from above 

 bearing some tubes of the lateral line, and becoming more elon- 

 gate and oblique anteriorly, until from the point of the pectoral 

 1872.] 



