FISHES OF FAMILY MICRODESMIDAE — REID 67 



shades of the upper row faintly invading the membrane of the base 

 of the dorsal fin; sides of the head and lower jaw indefinitely shaded 

 wdth brownish. 



Two specimens, 80 and 91 mm in standard length; the smaller from 

 a tide pool at Panama. Collected March 21, 1912, by Meek and 

 Hildebrand. U.S.N.M. no. 82678. The larger example, no. 82705, 

 collected at Chame Point, Panama, by Robert Tweedlie. 



Distinguished from all other species of the genus by the much 

 greater posterior insertion of the dorsal fin. 



MICRODESMUS mLDEBRANDI, new species 



Figure 9,/; Figure 11, c; Plate 2, Figure 6 



Microdesmus dipus (not Giinther) Meek and Hildebrand, Publ. Field Mus. 

 Nat. Hist., zool. ser., vol. 15, pt. 3, pp. 956-957, 1928 (Panama). 



Bod}^ elongate, compressed posteriorly; tail notably longer than 

 rest of body, its length to base of caudal fin 1.7 in total length. Head 

 short, 10.6 in standard length. Depth 20; predorsal 6.3; preanal 2.1; 

 preventral 10.2; ventral to vent 2.7; snout 4.9 in head measured to 

 upper angle of gill opening. Dorsal 55, anal 38, pectoral 10, ventral 

 1-3. Eye small, lateral, high. Interorbital rather broad, the space 

 between the eyes 3.7 in head. Mouth small, little oblique, reaching 

 about to anterior edge of the eye. Lower jaw^ strongly projecting; 

 lips fleshy, with pronounced lateral flanges, the free margin of which is 

 confined to the side of the head. The frontal region and lower jaw 

 with pronounced longitudinal swollen muscular folds or ridges; the 

 former extending from interorbital region to tip of snout; the latter 

 from tip of lower jaw to posterior end of mandible. Anterior nostril 

 situated in a minute round pore at the oral end of the frontal ridges; 

 posterior nostril slightly larger and situated above and before the eye. 

 Teeth small, even, close-set, in two irregular series in the jaws; vomer 

 and palatines tootliless. Gill openings restricted laterally, extending 

 from base of the middle pectoral rays obliquely downward and forward 

 to slightly below and before the lower pectoral ray, the apertures 

 slightly longer than width of the base of pectoral fin. Body and 

 head, except snout and lower jaw, covered with minute scales im- 

 bedded in the sldn ; at the base of the dorsal and anal fins the arrange- 

 ment of the scales is notably differentiated in that they are imbedded 

 in oblique rows extending outward and backv/ard on a longitudinal 

 narrow flat plane extending the full length of the fin bases. Scales 

 with 24 radiating striae. Myomeres evident, 20 body and 31 caudal = 

 51 muscular impressions. Vertebrae, 19 body and 37 caudal=56. 

 Vertical fins long and low, confluent with the caudal fin at base. 

 Origin of dorsal fin above tip of pectoral. Anal similar to but shorter 



