American' East Coast Arc as 51 



wholly co^■ered b}' the ligament and usually with numerous fun'ows for the resiliuni 

 forming concentriclozenges ; teeth similar, in a long, uninterrupted series, slightly larger 

 and more oblique distally; valves equal and similarly sculptured; epidermis usually pilose 

 and profuse. 



"The young shell is often and the adult sometimes auriculate behind. The transition 

 to Scapharca s. s. is very gradual and complete." — Dull, 1898. 



Area subrostrata Conrad 

 Plate XII, Figures i, 3, 3, 4 



Area subrostrata Conrad, Acad. Nat. Sci. Phila., Proc, vol. i, p. 30, 184T; Journ., ist. ser., vol. 8, 



pt. 2, p. 185, 1842; Fos. Med. Tert., p. 58, pi. 30, fig. 7, 1845. 

 Not Area subrostrata Sowerby, Quart. Journ. Geol. Soc. Lond., vol. 3, pp. 413, 418, pi. 15, tigs. S, 



9, 1847. 

 Scapharca tennicardo Conrad, Am. Journ. Conch., vol. 5, p. 39, pi. 2, fig. 4, 1869. 

 Scapharca {Area) subrostrata Conrad, Acad. Nat. Sci. Phila., Proc. for 1862, p. 580, 1863. 

 Scapharca (Auadara) subrostrata Dall, Wagner Free Inst. Sci., Trans., vol. 3, pt. 4, p. 655, 1898. 

 Area (Scapharca) subrostrata Glenn, Maryland Geol. Surv., Miocene, p. 385, pi. 104, figs. 2, 3a, 



3b, 1904. 



"Ovate; profoundly ventricose; ribs about 30, little prominent, fiat, longitudinally 

 sulcated; posterior side produced, cuneiform; rounded at the extremity ; hinge linear in 

 the middle, teeth obsolete, except towards the extremities; within slightly sulcated; cren- 

 ulations of the margin sulcated in the middle. Length 2 inches." — Conrad, 184 1. 



Shell slightly inequivalve; beaks mesially sulcate; ribs twenty-nine to thirty-two, 

 each rib with a longitudinal sulcus and usually a shallower sulcus on each side of this, 

 dividing each rib into four riblets, sometimes more than four riblets posteriorly; central 

 ribs sometimes nodulous; interspaces usually narrower than the ribs; cardinal area with 

 five to eight concentric grooves; hinge-line short; older shells with central teeth obsolete 

 and distal teeth irregular. In the ribbing this species resembles A. dodona, but otherwise 

 the two species are distinct. It is evident that Scapharca tcmticardo Conrad, is a syn- 

 onym of A. subrostrata. This is one of the species that show the close relation between 

 the sections Scapharca and Anadara. The young has the characters of Scapharca, but 

 the old shell shows some of the characters of Atiada?-a. It is placed by Dall in the 

 latter group. 



Dimensions. — Lon.-f 15,-35; alt. +7,-29; semidiam. 14 mm. 



Occurrence. — Miocene of Maryland in Talbot and Calvert Counties, at Calvert Cliffs, 

 Skipton, Centreville, Plimi Point, and other localities. A single valve, stated to be 

 from the Miocene of North Carolina, is in the National Museum. — Dall. Calvert Mio- 

 cene of Chesapeake Beach, 3 miles south of Chesapeake Beach, Plum Point, Truman's 

 Wharf, White's Landing, Church Hill, 3 miles West of Centerv'ille, Reed's Wye Mills, 

 near Skipton. — Glenn. Miocene of Plum Point and Chesapeake Landing, Maryland. 

 — C. U. Museum. 



Area einia Glenn 



Plate XII, Figures 5, 6 

 Area [Scapharca) ehiia Glenn, Maryland Geol. Surv., Miocene, p. 386, pi. 104, figs. 4a, 4b, 1904. 



