356 SYSTEMATIC PALEONTOLOGY 



convex curve or shoulder just posterior to the tip of the beak. Strati- 

 graphically its occurrence is distinct from tliat of ohruta. since it has only 

 been found in beds lower in the Miocene series than those containing the 

 obruta. 



It differs from A. distans by being thicker and more convex, by hav- 

 ing more numerous and more angular undulations, by having a beak that 

 is less acute and prominent and more abruptly and strongly curved for- 

 ward. The A. distans cannot, moreover, be considered as the young of 

 this species. ' 



The few specimens obtained from Plum Point agree with the typical 

 ones from Jones Wharf except that they have a somewhat less strongly 

 undulated surface. They were found at Plum Point only in a very sandy 

 stratum close to tide level. ■ From this sand-loving characteristic it re- 

 ceives its name. 



Length, 30 mm. ; height, 26 mm. ; diameter, 7 mm. 



Occurrence. — Choptank Formation. Governor Kun (lower bed), 

 2 miles south of Governor Eun (lower bed). Flag Pond (lower bed), 

 Jones Wharf, Pawpaw Point, Cuckold Creek, Cordova, Greensboro. Cal- 

 vert Formation. Plum Point. 



CollecUons.—Mavy\&nd Geological Survey, Johns Hopkins University, 

 U. S. National Museum, Philadelphia Academy of Natural Sciences. 



Astarte perplana Conrad. 

 Plate XCIV, Figs. 10, 11. 



Astarte perplana Conrad, 1840, Fossils of the Medial Tertiary, p. 43, pi. xxi, tig. 3. 

 Antarte planutata [sic] Conrad, 184:i, Proc. Nat. Inst., Bull, ii, p. 187, (listed only). 

 Astarte perplana Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 578. 

 Astarte planulata Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 578. 

 Astarte perplana Meek, 1804, Miocene Check List, Smith. Misc. Coll. (183), p. 7. 

 Astarte planulata Meek, 1804, Miocene Check List, Smith. Misc. Coll. (183), p. 7. 

 Astarte (Ashtarotha) perplana Ball, 1903, Trans. Wagner Free Inst. Sci., vol. iii, pt. 

 vi, p. 1493. 



Description. — "Shell triangular, inequilateral, much compressed; disks 

 coarsely wrinkled and obscurely undulated ; posterior side subcuneiform ; 

 extremity rounded ; beaks prominent, acute, with angular grooves ; lunule 

 long, elliptical; inner margin crenulated." Conrad, 1840. 



The strength of the undulations is somewhat variable; shell rather 

 thick and solid ; inner margin crenulated or smooth. 



Length, 36 mm. ; height, 29 mm. ; diameter, 6 mm. 



