332 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



in eacii jaw only. Nostrils clonble, distant, the anterior near the end 

 of snout, the posterior above anterior margin of orbit. Gill-opening a 

 very narrow, somewhat oblique slit, from front of lower third of pec- 

 toral tin downward and forward. Branchiostegals evident, 4 or 5 in 

 number. Eye very small, lateral, situated near the upper profile of 

 the head, its diameter nearly half the length of the short snout. 



Vertical fins well developed; dorsal and anal connected with the 

 caudal by a very delicate membrane. Distance from origin of dorsal 

 fin to occiput three times the length of the head, its rays distant, con- 

 nected by thin transparent membrane, as are the rays of the anal; most 

 of the rays simple and undivided (but articulate) ; a few of the posterior 

 only forked at tip. Origin of anal fin nearly equidistant between gill- 

 opening and tip of caudal, its rays mostly forked at tip. Caudal rays 

 much divided and more closely set than those of dorsal and anal, the 

 fin somewhat pointed in outline, as long as the head. Tail not isocer- 

 cal, truncate at base of caudal fin. Ventral fins very small, close to- 

 gether, inserted slightly behind base of i)ectorals; each fin reduced to 

 a single undivided filament. Pectoral fins snmll, pointed; the middle 

 rays longest, much shorter than the ventrals and half the length of 

 the head. 



Vent considerably behind middle of total length of the fish (with 

 caudal). 



Head and body covered with scattered rudimentary scales. 



Head 14 J in length; greatest depth 15'|. D. 48; A. 29; 0. 3-17-3; 

 P. 13; V. 1. 



Color in life translucent light olive, with a series of irregular quadrate 

 dark blotches along the back and a series along each side, these blotches 

 formed of clusters of dark points. 



One specimen, nearly 4 inches in length, was taken in a rock-pool at 

 Panama. 



This si)ecies differs from the description of the previously known 

 Microdesmus dipus Gthr. in the posterior insertion of the dorsal and of 

 the posterior position of the vent, the smaller number of fin rays, the 

 shorter head, longer ventrals, and mottled coloration. 



18. Cerdale ionthas, gen. et sp. nov. (296(54.) 



Char, gen.— Allied to Microdesmus Giinther, from which genus it is 

 distinguished by the presence of two rays in the ventral fin. Its body 

 is much less elongate than in Microdesmus. The gill-openings are re- 

 duced to small, nearly horizontal slits below and in front of the pectoral 

 fins. The pseudobrauchijie are well developed and the tail is not iso- 

 cercal. 



Descr. spec— Body considerably elongate, compressed, of nearly 

 equal depth throughout, the head tapering rapidly from occiput to 

 snout; snout short, not obtuse, but the lower jaw heavy and blunt, 

 much projecting beyond the preuiaxillaries; gape very short and 



