140 THE CYPRINODOXTS. 



Bivulus isthmensis sp. n. 



D. 9 ; A. 11 ; V. 6 ; P. 15 ; LI. 32 ; Ltr. 8. 



Elongate, compressed posteriorly, depressed forward. Head liroad, much 

 depressed, flattened on the crown, three tenths of the length without the 

 caudal. Snout medium, blunt, half as long as the eye. Eye one third of the 

 head, twice the snout, less than the interorbital space. First ray of the dor- 

 sal over the middle of the base of the anal, two thirds of the distance from 

 the head to the base of the caudal. Fii-st ray of anal midway from head to 

 caudal, last ray nearly as far back as that of the dorsal. Caudal elongate, 

 pointed, as long as the head. 



Light olivaceous, with a dark blotch at the base of the dorsal and an- 

 other on the back above or in front of the first ray of the anal. Apparently 

 there is a light transverse streak at the base of the caudal. 



Rio San Jose, Costa Rica. 



Rivulus obscxirus sp. n. 



D. 6 ; A. 8 ; V. 6 ; P. 12 ; LI. 29 ; Ltr. 8. 



Moderately slender, shaped like M. cylindraceus. Head broad, flat on the 

 crown, much wider than deep, three elevenths of the length to. the caudal. 

 Snout broad, blunt, rounded, little more than half as long as the eye. Mouth 

 wide, lower jaw longer, upper short. Eye large, one tliird of the head, 

 twice the snout, two thirds of the interorbital space. Origin of dorsal 

 behind the base of the anal, three fourths of the distance from the middle 

 of the eye to the base of the caudal. Origin of anal half way from head to 

 caudal; about one half of the base is in front of that of dorsal. Ventrals 

 small, hardly reaching the anal. Caudal long, pointed, longer than the 

 head. 



Light brownish on the back ; with or without bro,wnish blotches, among 

 which, on each side of the vertebral line, there is a series of three or more 

 light blotches. Snout whitish on the top ; occiput dark. 



Lake Hyanuary. 



Rivulus atratus sp. n. 



B. 5 ; D. 6 ; A. 9-10 ; V. 6 ; P. 11 ; LI. 81 ; Ltr. 7. 

 Elongate, rather slender, depressed forward, compressed behind the vent 

 somewhat less than in any of the other species, depth about one sixth of the 



