1 89 PALEONTOLOGY OF NEW-YORK. 



PLATE Vlir. 

 Fig. 1 - G. Ventral valves, where the strias are nearly cijual or altetnatiug in size. 

 Fig. 7 & 8. Individuals presenting some variety in snrfacc characters. 



Fig. 9. A young shell with salient hinge extremities, and strongly elevated striae separated 

 by fascicles of finer strias between. 



Fig. 5 a. The upper figure with this number is an enlargement of the surface of fig. 9. 



Fig. 10. An individual with surface characters similar to the last, having the hinge extremi- 

 ties rounded, and the hinge line a little shorter than the greatest width of the 

 shell below. 



Fig. 11. Interior of a ventral valve. 



Fig. 11 a ( by error 12 a) above last figure. An enlargement of the area and crenulations. 



Fig. 12 & 12 a. Interior of ventral valve, and enlargement of area. 



Fig. 14 & 16. Casts of the interior of the ventral valve, where the shell is but partially 

 exfoliated. 



Fig. 15 & 15 a. The interior of a ventral valve, and enlargement of a portion of the same. 

 In this specimen the hinge line has been broken, and the flabellate vascular 

 impressions almost obliterated in the process of cleaning the shell. 



Fig. 16, at right hand of page. A portion of the surface much enlarged, showing the nearly 

 equal striae, crossed by finer concentric lines. 



The specimens figured on Plate viil are from the Teutaculite limestone and base ot the 

 Pentamerus limestone; and at the time they were engraved in 1849, wers supposed to 

 represent the species decribcd bj' Mr. Conrad as cited above. 



PLATE XVL 



Fig. 1 a. A young individual slightly convex in the centre towards the beak, and flat at the 

 sides. 



Fig. 1 b. Profile showing the outline from beak to base. 



Fig. 1 c. Enlargement showing the stronger elevated striae with the finer intermediate ones, 

 and the commencement of other stronger ones in the midst of the finer striae. 



Fig. 2. An individual of the same character, having a greater convexity near the beak. 



Fig. 3 «. A similar form where the beak or umbo is not elevated, and the whole shell nearly 

 flat. 



Fig. 3 b. Profile showing the curvature of the shell near the base. 



Fig. 3 e. Enlargement of striae, showing the fasciculate character. 



Fig. 3 el. A farther enlargement of the surface, showing the concentric striae. 



Fig. 4 a. An individual having the character of S. rec'ilateris. 



Fig. 4 6. Profile of the same. 



Fig. 4 e. Profile of an individual having similar characters of surface, with a greater con- 

 vexity. 

 Fig. 4 d. Enlargement of striae of 4 a, showing the alternating size and frequent bifurcation. 

 Fig. 5 a. The &'. imprena of Conrad, natural size. 

 Fig. 5 b. Profile of same, showing the abrupt bending or geniculation towards the base. 



Fig. 5 f. Enlargement of striae, showing the coarser ones with intermediate fascicles of 

 smaller ones. 



Fig. 5 rf. A portion of the surface enlarged where partially exfoliated on an impression of 

 the exterior surface, showing the impressed lines made by the stronger striae ; 

 which is merely a reverse of fig. 5 d, or of fig. 3 c & 3 </. 



