294 PALEONTOLOGY OF NEW-YORK. 



350. 8. AMBONYCHIA CARINATA. 



Pl. LXXX. Figs. 5 a, b. 



Pterinea carinatn. Goldfuss, Petrefacta, Vol. ii, pag. 136, pl. 119, fig. 9. 

 Not Pterinea carinata of Conrad, Vanu.\em and Emmons, loc. cit. 



Shell ovate, oblique, ventricose ; anterior margin abruptly declining from the beaks, and 

 rounded below ; posterior margin oblique, expanded, scarcely alate ; beaks acute ; cardinal 

 margin short ; surface marked by about twenly-four equal rounded radii, which are slightly 

 oblique, in a direction from the posterior margin above, to the anterior margin below ; radii 

 equal to the interspaces. 



The specimen figured and described has the shell nearly or entirely removed, so that 

 the finer concentric striae, which doubtless existed, cannot be discovered. This species is 

 more ventricose than the preceding, the radii stronger and fewer in number, and they 

 have an oblique direction, which is not noticed in that species. I have seen one or two 

 other similar specimens, leaving no doubt of the permanency of the characters which 

 clearly distinguish it from the last. This is probably identical with the one described by 

 GoLDFuss, who cites " Lewistown in Oneida country," as its locality; and the rock, " the 

 Graywacke," is doubtless the argillaceous sandstone of the Hudson-river group. There 

 has heretofore existed some doubt whether the common species of this group was the one 

 described by Goldfuss ; and since the discovery of another more nearly resembling the 

 figure of that author, we may reasonably conclude the latter to be the true Pterinea carinata. 



Fig. 5 a. Left valve of this species. 



Fig. 5 b. Profile view, showing both valves. The apparent incquaUty of the beaks is produced by a 

 slight displacement from pressure. 



Position and locality. All the specimens of this species which have fallen under my 

 observation are from loose masses of the rock ; but its association with Cyrtolites ornatus, 

 and other well known fossils of the group, leaves no doubt of its true position. 



351. 11. MODIOLOPSIS MODIOLARIS. 



Pj.. LXXXI. Figs, ia- g; Pl. LXXXll. Fig. 1. 



Pterinea modinlaris. Conrad, Ann. Geol. Report, 1838, p. 118; 1839, p. 63. 

 Cypricardites modio/aris, and C. atigitstifrons. Conrad, Ann. Geol. Report, 1841, p. 52. 



— ovaia. Conrad, Ann. Geol. Rep. New- York, 1841, p. 52. 



— ovata. Emmons, Geol. Report, 1842, pag. 405, fig. 2. 



— anguslifrotis. Id. lb. pag. 405, fig. 1. 



Not Cypricardites niodiolari^, Emmons, Geol. Report, 1^12, pag. 403, fig. 4. 



Compare Modiola (Tpansa, Portlock, Geol. Rep. Londonderry, pag. 425, pl. 33, fig. G. 



Somewhat obliquely oblong-ovate, narrowed before, expanded and obliquely truncated 

 posteriorly ; liasal margin usually contracted, or slightly arched upwards ; cardinal line 

 extended, straight or slightly curved ; beaks moderately prominent, near the anterior 

 extremity; an oblique scarcely defined ridge, extending to the posterior basal margin; 



