14. HETERODONTID^E - GYROPLEURODUS. 33 



"Iii the latter genus, the branches of the lower jaw are at lirst con- 

 tiguous and diverge from each other at an acute angle, while in front of 

 the oblique whorls of molars, and between the acute teeth of the front 

 which encroach on the sides, a cordiform area exists. The lateral or 

 molar teeth are numerous, and arranged in oblique whorls, which rapidly 

 increase in size to the fifth, behind which they again decrease. The 

 branchial apertures are also comparatively large, the first being longer 

 than the length of the branchial region. 



"In GyropleuroduSj the- brandies of the lower jaw are widely separated 

 by an interval rounded in front and becoming wider behind, the sides 

 themselves being curved outwards; the acute teeth are confined to 

 the front and the molar teeth are few and disposed in about four whorls, 

 the first three of which slightly increase, while the fourth is almost 

 rudimentary. The branchial area is almost oblong." 



Head short and high, broad, but with subvertical sides; the forehead 

 very declivous from eyes, and with the snout wide and transverse, but 

 prominent; two blunt, diverging ridges are continued from each side of 

 the snout and abruptly merge into the more conspicuous superciliary 

 ridges, the interval between which is nearly plane ; teeth in front digi- 

 tated, with three or four cusps, quiucuncially distributed in rows slightly 

 converging toward the middle; in the upper jaw, on the sides, molars 

 oblong and flattened, arranged in about four oblique whorls, uniform or 

 increasing backward, except the last, which is smallest; on the sides of 

 iihe lower jaw, also, are molars oblong, with flattened crowns, and arranged 

 in transversely oblique whorls, but decreasing backward (Gill). One 

 species known. (YL>{><>-, ring or whorl; -nhupw, side; oi><n^ 1 tooth.) 



41. <K. fvaBscisci (Grd.) Gill. 



Dorsal fins considerably produced backward at their posterior angle; 

 the compressed spine forming about half of the base of each fin ; anal 

 fin large, directed very obliquely backwards, reaching the root of caudal ; 

 caudal fin forming about one fourth of the length; color brownish, varie- 

 gated with sparsely scattered small black spots all over the body and 

 fins. Coast of California (Gill}. 



(Cctfracion francisci Girard, Pro<;. Ac. Nat. Sci. Phila. 1854, 196; Ccstradon fmncisco 

 Giiutlier, viii ? 41G ; Gill, Proc. Ac. Nut. Sci. Phila. 1862, 492.) 



Bull. Nat. Mus. No. 16 - 3 



