4«S PAL5:0NT0L00Y OF NEW-YORK. 



Spirit'er pyxfdatus ( n. s.)- 



PlATB C. Flo. 9 - 12. 



Shell semiellipticcal in outline, one side angularly gibbous in the middle ; 

 cardinal line equalling ( sometimes a little greater or less than ) the 

 greatest width of the shell. Ventral valve with a narrow mesial sinus, 

 in the summit of a broad strong elevation ; the beak abruptly incurved 

 over a narrow linear area, which extends to the cardinal extremities ; 

 foramen of moderate width, with strong divergent dental lamellae. 

 The muscular impressions are well marked, and sometimes there is a 

 thickened process from the interior filling the summit of the foramen. 

 Dorsal valve flat at the sides and near the beak, with a broad depression 

 below, in the centre of which is a narrow mesial elevation. The mar- 

 gins of the shell on each side present a few undulations or marginal 

 folds, and, in rare examples, these reach half way to the beak. 



The surface, in its perfect condition, has been concentrically striated, 

 with finer longitudinal striae. 



This small species occurs in the Oriskany sandstone of New-York, in the condition 

 of casts, and, from its small size and peculiar form, had not been very satisfactorily 

 determined. Some specimens of the shell from Cumberland ( Maryland ) preserve 

 the characters showing the structure of a true Spirifer ; while the exterior, in its 

 general expression, departs from the ordinary forms of this genus. 



Fig. 9 a. Dorsal view of a specimen of this species. 



Fig. 9 b. Ventral view of the same. 



Fig. 9 c, d. Profile and front views of the same. 



Fig. 10. The interior of the ventral valve, showing the area, etc. 



Fig. 11. The cast of the ventral valve. 



Fig. 12. A cast of the dorsal valve. 



Geological position and localities. In the Oriskany sandstone : Albany and Scho- 

 harie counties ( New- York), and Cumljcrland ( Maryland ). 



