SOUTH AMERICAN NEMATOGNATHI. 143 



Snout blunt, decurved; upper jaw a little produced. 

 Teeth all villiform, those on the vomer forming two small, 

 separate, ovate patches which are contiguous to the twice or 

 thrice as large palatine patches. 



Gill-membranes forming a fold across the isthmus. Gill- 

 rakers 6-1-9. 



Pectoral pore large; vertical series of pores on the sides. 



Distance of dorsal spine from the snout 2^-2^ in the 

 length; the spine of the dorsal and pectoral fins granular 

 on the basal half of their outer margins; the inner margins 

 serrate almost their entire length ; the spines equally long 

 1| in head. Distance of adipose fin from the dorsal 85 in 

 the length, the adipose more than half as long as the dorsal 

 fin, its posterior margin free. 



Caudal deeply forked, the upper lobe longer, somewhat 

 falcate, 3|-4 in the length. 



Anal fin about as long as high, deeply emarginate, its 

 highest ray 2\ in the head. 



Ventral fins not reaching the anal, 2 in the head. 



Top of head and dorsal surface dark blue with metallic 

 lustre, becoming silvery below; lower caudal lobe dusky; 

 basal half of the inner surface of the paired fins black. 



Head Sf-S^; depth 5|-5^; D. I, 7; A. 18. 



111. Tachisurus coerulescens (.Guuther). 



112. Tachisurus guatemalensis (Giiutber). 



113. Tachisurus assimilis (Giinthei). 



114. Tachisurus surinamensis (Bleeker). 



115. Tachisurus dasycehpalus (Giinther). 



116. Tachisurus longicehpalus sp. uov. 



Type, No. 4972. One specimen, 1^; length .29 m. Panama. Steiu- 

 dachnei'. 

 Elongate, slender; greatest width little greater than 

 depth. Head long and depressed, its greatest width 1^ in 

 its length, its greatest depth little more than half its length. 

 Top of head obscurely granular, the granules almost en- 

 tirely concealed by the skin; interorbital area flat and with 



