18S7.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 613 



JDiagnosis. 



Acautbopterygians with a depressed, broad, distegous crauiura, the 

 medifrontines double, plaue, sculptured, aud perfectly ecariiiate; the 

 sphenotlcs with the upper surface plaue and scarcely declivous; the 

 })arethmoids exserted, with the upper surface uearly contiiuious with the 

 mcdifroutiues aud the lower with the parasphenoid, and iui perforate; the 

 inoscthmoid with a large aud uearly square tabular surface aud a short 

 declivous i^ortion at a very obtuse augle with the former; the supraocci- 

 pitine with au anterior ecarinate plane portion and a posterior cristiform 

 portion ; the lateral posterior crests very low, depressed, and ceasing at 

 the mcdifroutiues; the hasioccipitliie solid below; the exoccipitme con- 

 dyles distant from each other; the parasphenoid very broad and ecari- 

 nate; the contour of the body fusiform; the head wedge-shaped aud 

 broad; the scales small aud cycloid; the caudal fin with procurrent ray- 

 lets; dorsal flu long aud preceded by free spines recliuable iu grooves, 

 aud normal pectoral aud ventral tins. 



Description of external characters. 



Body elongate, with a fusiform contour, gradually taperiug into a 

 stout and contracted caudal peduncle, and widening forwards towards 

 the head. 



Anus submedian, or slightly iu advance of the middle. 



Scales very small, cycloid, smooth, and closely adherent to the skin. 



Lateral line indistinct and nearly parallel with the back. 



Read cuneiform, oblong conic in profile and wide and oblong above, 

 with ihe epicranial muscles atrophied, aud consequently the bones of 

 the cranium apparent through the skin, revealing a sculptured or stri- 

 ated surface. 



Eyes within the anterior half of the length, entirely lateral and below 

 the profile, and of small size. 



Nostrils normal, the apertures on each side divided by a narrow 

 bridge. 



Mouth with a moderately oblique, lateral cleft. 



Jaws normally developed; the intermaxilUnes with short laminar ped- 

 icles, tapering branches distinct from the articular facets, and obliquely 

 set, thus leaving a triangular interval in front, with indentations at the 

 bases of the pedicles; tha supramaxillines y^idQwxng behind and down- 

 wards, and partially withdrawing under the preorbitals; mandible rather 

 low, and contracted behind the symphysis, and articulating under the 

 eye. 



Teeth small, acutely conic, iu broad bands on the jaws, vomer, pala- 

 tine, and tongue. 



Lips thin, normally developed. 



Tongue moderate. 



iSuhorbital bone normally developed, the preorbital extending for- 

 wards. 



