NATURAL SCIENCES OF PHILADELPHIA. 259 



Dorsal fins two. I. Agonin^e. 

 Body compressed and elevated towards the front. 

 Head continuous with back, parallelopiped and compres- 

 sed like Trigla, Podotkeci. 

 Dorsal fins separated ; first remote from nape, 1. Podothecus. 

 Head separated from back by a deep nuchal depression, Hypsagoni 

 Dorsal fins separated, 2. Hypsagonus. 

 Body elongated and not elevated, Agoni. 

 First dorsal behind nape. 



Breast granulated, 3. Hippocephalus. 

 First dorsal remote from nape. 



Lower jaw received within upper. Dorsal fins contiguous. 



Thoracic plates four, forming a square, 4. Agonus. 



Thoracic plates numerous, 5. Paragonus. 

 .Taws subequal, 



Body thick. Vomerine and palatine teeth, 6. Agonopsis. 



? Body compressed, 7. Leptagonus. 



Lower jaw longest. Dorsal fins contiguous, 8. Brachyopsis. 



Dorsal fin single, II. Anoplagonin.^. 



Teeth on the jaws alone, 9. Aspidophoroides. 



Teeth on the jaws, vomer and palatines, 10. Anoplagonus. 



Genus PODOTHECUS Gill. 



Syn. Podothecus Gill, Proc. Academy of Natural Sciences of Phila., vol. xiii. 

 p. 77, 1861. 



Body much compressed anteriorly and with the width subequal, or imper- 

 ceptibly decreasing to the caudal fin. The caudal peduncle is slender, sub- 

 equal and depressed. The dorsal outline is sigmoidally incurved towards the 

 peduncle. The breast is flattened, triangular, covered with a median and, 

 on each side, a lateral row of moderate plates ; the central plates are hex- 

 agonal. Head parallelopiped, much compressed, and with the width subequal. 

 Profile with a very decided oblique sigmoidal curve. Superciliary and occipi- 

 tal crests well developed and spinigerous. Temporal crests lateral. Snout 

 prominent, depressed, and with two spines on each side, one horizontal and 

 the other vertical or recurved. Mouth wholly inferior, with the periphery 

 oblong semi-oval. Lower jaw received within the upper. Teeth villiform, 

 present only on the jaws. Angles of mouth furnished with numerous barbels. 

 Dorsal fins separated by about three plates ; the first, commencing behind the 

 fourth pair of plates, is oblong but rather high, and sustained by about 

 nine slender spines. The ventral fins are closely approximated and received 

 in a longitudinal lanceolate groove. Each fin has apparently a spine and two 

 simple rays. 



Podothecus peristethits Gill. 



The form of this species is quite similar to that of a species of Peristethus or 

 Peristedion. The height is somewhat greatest just behind the bases of the 

 pectoral fins, where it equals the distance between the rostral spine and the 

 orbit ; thence it quite regularly diminishes, but with a slightly sigmoid dorsal 

 curve, the decrease being more rapid between the ends of the first and second 

 dorsal ; behind the latter it is much depressed and wider than high ; the 

 height very slowly diminishes towards the caudal. The greatest height equals 

 46-100 of the head's length ; that behind the first dorsal, 37-100 ; in front of 

 the anal, 32-100 ; and behind the second dorsal, 20-100. 



The width very regularly and slowly decreases towards the caudal. In front 

 of the bases of the pectorals it equals the height, or 48-100 of the head's 

 length ; behind the first dorsal it is less than the height at the same place, 

 1861.] 



