LAMELLIBRANCHIATA. 437 



LUNULICARDIUM CDRTUM. 



PLATE LXXI, FIGS. l»-23. 



Lunvlicardium curtum, Hall. Prelim. Notice Lamellibranchiata, 2, p. 97. 1870. 



" " " Pal. N. Y., vol. V, pt. 1. Plates ami Explanations : PI. 71, figs. 18-23. 1883. 



Shell below the medium size, ovate, sub-trigonal ; length usually a little less 

 than the height. Anterior and basal margins regularly curving. Entire 

 length of the posterior side truncate, with a narrow alation along the margin. 



Valves, in well-preserved specimens, regularly convex below, becoming 

 gibbous in the middle and above. 



Beaks anterior to the middle, prominent, incurved and directed forward. 



Surface marked by from twenty-five to thirty regular, narrow, rounded or 

 sub-angular plications, with wider interspaces, and by fine lamellose concen- 

 tric striae, which arch upward on the plications. Some specimens show a 

 pustulose character of the surface as indicated in fig. 23 of plate Ixxi. 



Three specimens measure respectively 13, 20 and 23 mm. in length, and 

 14, 18 and 24 mm. in height. 



This species differs from L. rude in its greater height, larger number of plica- 

 tions and more delicate characters. As compared with L. ornatum, it has a pro- 

 portionally much longer posterior truncation, and fewer and narrower plications. 



Formations and localities. In the Marcellus shale at Alden, Erie county, N. Y., 

 and in the Hamilton shales on the shores of Cayuga and Seneca lakes, and at 

 Pratt's falls, TuUy and Hamburg, N. Y. 



L0NULICAEDIUM OKNATUM. 



PLATE LXXI, FIGS. 25-32. 



Pinnopsls onrntux. Hall. Geol. Suiv. N. Y., Rep. Fouith_Dist., p. 244, t. 180, fig. 8. 1843. 

 iMntdicardimn (yniatmii, Hall. Prelim. Notice Lamellibranchiata, 2, p. 97. 1870. 



• ' " " Pal. N. Y., vol. V, pt. 1. Plates and Explanations : PI. 71, figs. 25-29. 1883. 



PiniunmU ai.iiliroiitra, " Oeol. Surv. N. Y., Rep. Fourth Dist., p. 244, t. lOG, fig. 7. 1843. 



LimulicanUiim aciUironlruin, Hall. Prelim. Notice Lamellibranchiata, 2, p 97. 1870. 



<• " " Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 71, figs. 30-32. 



Shell large, broadly obovate, truncate upon the posterior side. Anterior and 

 basal margins regularly rounded, recurving abruptly at the posterior. 

 56 



