2450 Bulletin 4.7, United States National Museum. 



928. MICRODESMUS, Giinther. 



Microdesmus, GUNTHER, Proc. Zool. Soc. London 1864, 26 (diput). 



Body anguilliform, covered with rudimentary scales ; head small, with 

 short, obtuse snout and small mouth ; lower jaw projecting; teeth minute, 

 in jaws only; eyes very small; gill opening reduced to a very narrow, 

 somewhat oblique slit, in front of lower part of pectorals; vertical fins 

 well developed, the dorsal and anal joined to the caudal by a thin mem- 

 brane; rays of dorsal mostly articulate, all but a few of the last simple; 

 ventral tins very small, reduced to a single ray; pectorals moderate; vent 

 normal, in middle of body. Pacific coast of tropical America, (jutnpos, 

 small; d Erf/nog, a band.) 



a. Dorsal rays 55, the fin beginning less than a head's length behind occiput. 



DIPUS, 2808. 

 aa. Dorsal rays 48, the fin beginning more than a head's length behind the occiput. 



KETROPINNIS, 2809. 



2808. MICRODESMUS DIPUS, Giinther. 



Head about 11 in total length ; depth about 18. D. 55 ; A. 34 ; C. 16 ; P. 12 ; 

 V. 1. Head rather compressed, snout short, mouth very narrow, lower 

 jaw very prominent. Eye minute, lateral, and in anterior third of head. 

 Dorsal fin commencing at a distance from occiput which is somewhat less 

 than length of head, nearly even, the rays very distinct, the interradial 

 membrane being thin and transparent; anal fin commencing immediately 

 behind vent. Caudal rays much more slender and more closely set than 

 those of dorsal and anal ; caudal fin rounded, length of head ; pectorals as 

 long as ventrals, and as long as head ; ventrals close together, and inserted 

 a little behind root of pectoral. Upper parts uniformly brownish olive. 

 Panama. Known from a single specimen, 4| inches long* (Giinther.) (<5z's, 

 two; 7tov$, foot.) 



Microdesmus dipus, GUNTHER, Proc. Zool. Soc. London, January 26, 1864, 4, pi. 3, fig. 2, 

 Central America (Coll. Capt. Dow) ; JORDAN, Cat., 126, 1885. 



2809. MICRODESMUS RETROPIXNIS, Jordan & Gilbert. 



Head 14 in length ; greatest depth 15f. D. 48 ; A. 29 ; C. 3-17-3 ; P. 13 ; 

 V. 1. Body very elongate, compressed, tapering somewhat from front of 

 dorsal to caudal peduncle. Head very small, rapidly tapering forward 

 from occiput ; upper profile with a noticable depression behind the orbits, 

 the outline thence to snout strongly convex. Mouth very small, some- 

 what oblique, the fleshy tip at symphyeis of lower jaw projecting much 

 beyond the premaxillaries; gape scarcely reaching vertical from orbit. 

 Teeth small, apparently in a single series in each jaw only. Nostrils 

 double, distant, the anterior near the end of snout, the posterior above 

 anterior margin of orbit. Gill openings a very narrow, somewhat oblique 

 slit, from front of lower third of pectoral fin 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 the 

 length of the short snout. Vertical fins well developed j dorsal and anal 



