308 
PALAEONTOLOGY OF NEW YORK. 
Microdon (Cypricardella) bellistriatus. 
PRATE XLII, FIGS. 17-20; PRATE RXXIII, FIGS. 7-22; AND PRATE RXXIV, FIGS. 5-10. 
Microdon bellastriata, Conrad. Jour. Acad. Nat. Sci., Phila., vol. viii, p. 247, pi. 13, fig. 12. 1842. 
“ “ “ Hall. Geol. Surv. N. Y., Rep. Fourth Dist., p. 196, fig. 2. 1843. 
“ “ “ Rogers. Geol. Pennsylvania, p. S27. 18(j8. 
“ “ “ Hall. Twenty-third Rept. N. Y. State Cab. Nat. Hist., pi. 14, fig. 8. 1873. 
■“ “ “ “ Prelim. Notice Lamellibranchiata, 2, p. 31. 1870. 
Eodon bellistriatus (Conrad), S. A. Miller. Cat. Amer. Pal. Foss., p. 244. 1877. 
Microclonella bellistriata (Conrad), GEhlert. Mem. Geol. Soc., France, Third Ser., tom. ii, p. 27, pi. 4, figs. 
4a, 4b. 18S1. 
Microdon ( Microdonellci ) ( Eodon ) bellistriatus (Conrad), Hall. Pal. N. Y., vol. v, pt. 1. Plates and 
Explanations : PI. 73, figs. 7-22 ; pi. 
74, figs. 4-10. 1883. 
Compare Sanguinolaria lamellosa, Goldfuss. Petrefacta, vol. ii, p. 279, pi. 59, fig. 12. 1834-1840. 
Shell of medium size or larger; form sub-rliomboidal 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-tliird 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 
rounded 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-line. 
Umbo sometimes moderately convex. Umbonal slope continued as a low 
undefined ridge to the post-basal angle. 
Test of moderate thickness, marked by strong, even, angular strise, which 
continue of nearly uniform character over the entire shell, and are subdued 
in specimens from the softer shales. 
Anterior muscular 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. 
