1885.] PROCEEDIXGS OF UNITED STATES NATIONAL MUSEUM. 69 



depressed, and the supraoccipital crest more developed than in most of 

 the others. In all these respects Percina is intermediate between Perca 

 (HI the one hand, and the extreme forms, Ammocrypta and Mioroperca^ 

 on the other. 



The other Darters form two irregular lines, the one with dej^ressed 

 cranium, and slenderer bones, culminating in Ammocrypta; the other 

 havijig the cranium more convex transversely, the bones firmer and ^ 

 smooth, and the vertebra? fewer in number. This grouj) seems to cul- 

 minate in Microperca. 



2. Hadropterus aspro, Cope & Jordan. 



This species has the skull smoother than in Percina^ its surface more 

 convex transversely 5 frontal region very narrow, grooved 5 parietals 

 slightly striate, somewhat depressed behind the eyes, but less than in 

 Boleosoma. Supraoccipital large, its crest reduced to a minute process. 

 Profile essentially as in Percina. Bones of shoulder-girdle and pharyn- 

 geals essentially as in Percina. Pyloric cceca, 4. Vertebrge, 19 -4- 23 

 = 42. 



3. Hadropterus scierus, Swaiu. 



Skull essentially as in H. aspro. Vertebrae 18 -f 22 = 40. 



4. Hadropterus evides, Jordan «fe Copeland. 



Skulj essentially as in H. asjjro, the parietal region a trifle smoother 

 and a little more convex transversely. Vertebrae 18 + 22 = 40. 



5. Hadropterus phoxocephalus, Nelson. 



Skull more elongate than in M. aspro, the frontal region very narrow. 

 Parietals smooth, somewhat depressed above, but rather strongly con- 

 vex transversely ; no supraoccipital crest. Suprascapula slender ; 

 scapula broad. Profile most prominent behind eye. Vertebra) 19 -f 

 20 = 39. Pyloric cceca 2. This species is chiefly peculiar in the nar- 

 rowness of the head. 



6. Cottogaster copelaiidi, Jordan. 



Skull short, the frontal region rather short and not very narrow. 

 Parietals faintly striate, • depressed above, little convex transversely. 

 Sutures distinct. Supraoccipital crest obsolete ; scapula btoad. Pro- 

 file most prominent above eye. Pyloric coeca 3. Vertebr;e 18 + 20 = 38. 



7. Ulocentra simotera, Cope. 



Skull not very narrow anteriorly. Parietal region rather depressed, 

 not strongly transversely convex, its bones faintly grooved. Frontal 

 region much broader than in Diplesion blennioides, the top of the head 

 much flatter. Profile highest above posterior margin of eye, scapula 

 rather broad. Supraoccipital crest small. Vertebrae 15 + 23 = 38. 



So far as the skull is concerned, this species more resembles Cot- 

 togaster than Diplesion. 



