294 PALEONTOLOGY OF NEW-YORK. 
350. 8 AMBONYCHIA CARINATA. 
Pu, LXXX. Figs. 5 a, bd. 
Pterinea carinata. Goupruss, Petrefacta, Vol. ii, pag. 136, pl. 119, fig. 8. 
Not Pterinea carinata of Conrap, VANUxEM 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 twenty-four equal rounded radii, which are slightly 
oblique, ina 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 
Goxtpruss, 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 Gotpruss; 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 inequality 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. 
Pu. LXXXI. Figs. 1 a- g; Pu. LXXXII. Fig. 1. 
Pterinea modiolaris. Conrap, Ann. Geol. Report, 1838, p. 118; 1839, p. 63. 
Cypricardites modiolaris, and C. angustifrons. Conran, Ann. Geol. Report, 1841, p. 52. 
— ovata. Conrap, Ann. Geol. Rep. New-York, 1841, p. 52. 
— ovata. Emmons, Geol. Report, 1842, pag. 405, fig. 2. 
—_ angustifrons. Ip. Ib. pag. 405, fig. 1. 
Not Cypricardites modiolaris, Emmons, Geol. Report, 1842, pag. 403, fig. 4. 
Compare Modiola expansa, Portiocx, Geol. Rep. Londonderry, pag. 425, pl. 33, fig. 6. 
Somewhat obliquely oblong-ovate, narrowed before, expanded and obliquely truncated 
posteriorly ; basal 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; . 
