S6 BULIvETlN 31 86 



nent square radii, on the anterior side sharp, recurved and crenulated ; lun- 

 ule very broad and cordate, deeply impressed ; hinge thick ; pit anterior to 

 the cardinal tooth small and profound. This is a fragment of the right 

 valve about 5-8ths of an inch long. 



Cardita bilineata (see pi. 31, fig. 8) 



(Fig'd, Jr. Phila. Acad., vol. i, pi. 13, fig. 9.) 

 Subrhomboidal, very inequilateral, with about twenty-four wide, flat- 

 tened radii, with very narrow interstices, a carina in the middle of each rib, 

 with an impressed line on each side of it ; ribs crenulated anteriorly ; carina 

 somewhat tuberculated on the posterior side of the shell. Length ^, 

 height 9-16. 



Cardita subquadrata (see pi. 31, fig. 7. ) 



Trapezoidal, compressed ; valves flattened in the middle ; radii about 

 twenty-five, broad on the disk, with very narrow interstices, and each rib 

 with a crenulated carina in the middle ; posterior to umbonal slope the ribs 

 are smooth, not carinated ; anterior short, rounded at the end ; posterior 

 margin obliquely truncated. Length 5-16. Height 7-20. 



Cardita subrotunda (see pi. 31, fig. 9) 



(Fig'd, Jr. Phila. Acad. vol. i, pi. 14, fig. 11.) 



Orbicular, inequilateral, ventricose, with about twenty-eight rounded 

 prominent, narrow radii ; ligament margin very oblique, short ; ends ob- 

 tusely rounded ; inner margin slightly crenulated. Length ^. Height K- 



Cardita vigintinaria (see pi. 31, fig. 10) 



(Fig'd, Jr. Phila. Acad., vol. i,pl. 14, fig. 12. 



Suborbicular, inequilateral, ventricose, with about thirty square radii, 

 about as wide as the interstices ; umbonial slope rounded ; anterior margin 

 subtruncated. Length ^. Height %. 



To these may be added blandingi of Conrad and iiifiatior of 



Meyer 

 Venericardia blandingi (see pi. 31, fig. 11, a) 



(Con., Jr. Phila. Acad. Nat. Sci., vol. 6, 1830, p. 229, pi. 9, fig. 20.) 



Shell suborbicular ; ribs about twenty, rather square with a rough 

 tuberculated carina on each ; anterior margin slightly truncated. 



This shell is very like Sowerby's V. carinata, but it is smaller, and 

 the carinae are not smooth ; it has been imbedded in a hard silicious matrix, 

 and the carinae are worn, except near the margin, where they are distinct. 



I am indebted to Mr. Morton for this fossil ; it was sent to him by 

 Dr. Blanding, of Camden, S. C. , who found it at Vance's Ferry in that state, 

 where other shells occur characteristic of the Maryland Upper Marine form- 

 ation. Cabinet of the Academy. 



