1 1 American Kast Coast Akcas 



markedly oblique: hinge-area broad, obscurely furrowed in longitudinal lines; beak 

 moderately elevated, incur\^ed, the apex directed backward; surface of the shell radiate- 

 ly ribbed, the ribs sinuous, beaded — especially on the anterior portion of the shell, 

 where they are separated by an intermediate fine line — becoming obsolete in the poster- 

 ior sulcus and on the wing where they are represented by two pairs of- lines; lines of 

 growth prominent towards the base and on the wing; basal margin crenulated. 



"Length 1.25 inches; height, from base to hinge-line, .5 inch. 



"This winged ark is at once distinguished from A. aviadajormis * ^ * by the ab- 

 sence of the anterior rostrum and its rectangular form. The last character, in addition 

 to differences in the ornamentation, also serves to distinguish it from the Miocene Area 

 incile. which resembles it somewhat in the pterination of the posterior slope — ."Heilprin, 

 1S87. 



"This very neat species appears to be somewhat rare, and has only been found in 

 the original locality as yet." — Ball. 



Ocairrence. — "Pliocene marls of the Caloosahatchie River, Florida." — Dall. 



Area bo'cC'deyiiana Dall; Plate II, Figure 3; (Wagner Free Inst. Sci., Trans., vol. 3, 

 p. 622, pi. 33, fig. 12, 1898) from the Oligocene of the Bowden beds, Jamaica and Plio- 

 cene of Limon, Costa Rica, is a small species with very anterior beaks and sculpture like 

 that of A. nmhonata and the diameter is greatest posteriorly. 



Subgenus Barbatia (Gray) Adams 



Barbatia Gray, Synops. Brit. Mus., 1840, p. (?); ibid , 1844, p. 81. Type Jlrca barhata L., II and 

 A. Adams, Gen. Rec. Moll., ii., p. 534, 185S. 



"The type form of this group is tolerably regular and seldom deformed, like the 

 typical Arks, from the anfractuosities of its station; the reticulated sculpture shows few 

 irregularities; the cardinal area is narrow with numerous grooves for the resilium, which 

 forms a series of elongated concentric lozenges on the area; the shell is not conspicuously 

 truncate or keeled ; the teeth are small and vertical in the middle of the series and 

 toward the end diverge distally and become larger and more distant. In some species 

 these distal teeth are often broken up, like those of Cucnllcea, but this feature is not con- 

 stant in the species. Several groups or sections are recognizable, though they range into 

 one another through their peripheral species. Such are the following: 



"Group of A. barbata'L. (Barbatia s. s.). This includes^. {B.) mississippiensis 

 Conrad from the Vicksburgian Oligocene. 



''Gvov.]}oi A. eandida GmeWn (Calloarea Gray, i8$-j,+P/agiarea Conrad, 1875). 

 This mc\ndes A. eHcti/Zoides Conrad {+ A. lima Conrad, 1847 not of Reeve, 1844,=^. 

 Conradi Desh,) from the Jacksonian; A. marylandica Conrad and ^. «/-«</« Heilprin, 

 Upper Oligocene and Older Miocene; and several other species. Litharea {lithodomus) 

 Gray, 1840, is probably based on a specimen of A. Candida, which had grown in the 

 burrow of a Lithodomus. Upper Cretaceous to recent. 



