MARYLAND GEOLOGICAL SURVEY 655 



Occurrence. MOXMOUTH FORMATION. Brightseat, Brooks estate near 

 Seat Pleasant, Friendly, 1 mile west of Friendly, Fort Washington, 

 Prince George's County. 



Collections. Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, Xew Jersey Geological Survey. 



Outside Distribution. Matawan Formation. Marshalltown clay marl, 

 Wenonah sand, Xew Jersey. Monmouth Formation. Xavesink marl, 

 Red Bank sand, Tinton beds, Xew Jersey. 



CRASSATELLITES PTEROPSIS Conrad 

 Plate XXXIX, Fig. 5 



Crassatella pteropsis Conrad, 1860, Jour. Acad. Nat. Sci., Phila., 2d ser., 



vol. iv, p. 279, pi. xlvi, fig. 9. 



Crassatella pteropsis Gabb, 1860, Ibidem, p. 395, pi. Ixviii, fig. 28. 

 Crasatella pteropsis Meek, 1864, Check List Inv. Fossils N. A., Cret and Jur., 



p. 11. 

 Crassatella (Pachythd'rus) pteropsis Conrad, 1869, Am. Jour. Conch., vol. v, 



pp. 47, 48. 

 Crassatella (Pachythtrrus) pteropsis Conrad, 1872, Proc. Acad. Nat. Sci., 



Phila., p. 50, pi. i, fig. 1. 

 Crassatella pteropsis Gabb, 1876, Ibidem, p. 310. 



Description. " Aliform, very inequilateral, convex anteriorly, poste- 

 riorly contracted ; umbonal slope slightly carinated below the umbo ; pos- 

 terior side rostrated ; surface with minute concentric, impressed lines, 

 very fine and closely arranged on the umbo and summit ; margin within 

 finely crenulated." Conrad, 1860. 



Type Locality. Owl Creek, Tippah County, Mississippi. 



Shell rather thin and compressed, not very large, very inequilateral, 

 posteriorly produced and alate in outline ; umbones flattened upon their 

 summits, orthogyrate, proximate, set back from the anterior extremity a 

 distance of approximately one-third the latitude; lunule and escutcheon 

 sharply defined, narrowlv lenticular, subequal in size, the portion of the 

 lunule in the right valve and of the escutcheon in the left valve shorter, 

 narrower and more strongly sculptured incrementally than the corre- 



