308 PALEONTOLOGY OF NEW YORK. 



MiCROUON (Cypricardella) bellistriatus. 



PLATS XLir, FIGS. 17-20; PLATE LXXIH, FIGS. 7-22; and PLATE LXXIV, FIGS. 8-10. 



Microdou bellaatriata, CoKRiv. Jour. Acad. Nat. Sci., Phila., vol. viii, p. 247, pi. 13, fig. 12. 1842. 

 " " " Hall. Geol. Sui-v. N. Y., Rep. Fourth Dist., p. 196, fig. 2. 1843. 



" " " R00BR.S. Geol. Pennsylvania, p. 827. 1868. 



•« " " Hall. Twenty-third Kept. N. Y. State Cab. Nat. Hist., pi. 14, fig. 8. 1873. 



" " " " PreUni. Notice Laniellibranchiata, 2, p. 31. 1870. 



Eodon bellistriatus (Conrad), S. A. Miller. Cat. Amer. Pal. Foss., p. 244. 1877. 

 Microdonella Mllitnata (Conrad), CEhlert. Mem. Geol. Soc., France, Third Ser., torn, ii, p. 27, pi. 4, figs. 



4a, 4b. 1881. 

 Microdoa (MicrodoyuUa) (Eodon) bellistrkUus (Conrad), Hall. Pal. N. Y., vol. v, pt. 1. Plates and 



Explanations : PI. 73, figs. 7-22 ; pi. 

 74, figs. 4-10. 1883. 

 Compai-e Sanguinolaria Iwnelhsa, Goldkcss. Petrefacta, vol. ii, p. 279, pi. 59, fig. 12. 1834-1840. 



Shell of medium size or larger ; form sub-rhomboidal to sub-elliptical ; pro- 

 portions of length and height extremely variable, varying from a length of 

 twice the height, to a length of less than one-third greater than the height ; 

 basal margin regularly curving anteriorly, often nearly straight in the poste- 

 rior half ; posterior margin almost vertically sub-truncate, sometimes gently 

 curving. Cardinal line nearly straight, sometimes slightly declining poste- 

 riorly, often arcuate. Anterior end narrowed, prolonged below and abruptly 

 I'ounded at the extremity ; constricted above by a distinct lunule. 



Valves depressed-convex, becoming moderately convex in the umbonal 

 region. 



Beaks usually at about the anterior third, but often nearer the anterior 

 extremity, small, closely appressed, scarcely rising above the hinge-liue. 

 Umbo sometimes moderately convex. Umbonal slope continued as a low 

 undefined ridge to the post-basiil angle. 



Test of moderate thickness, marked by strong, even, angular striae, which 

 continue of nearly uniform character over the entire shell, Jind are subdued 

 in specimens from the softer shales. 



Anterior mu.scular impression strong; posterior one superficial. Left 

 valve marked by a strong oblique fold or tooth, with a corresponding cavity 

 in the right valve. Posterior to this cavity are one or more obscure folds. 

 No lateral teeth proper have been observed. 



