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645 



TERTIARY FAUNA OF FLORIDA 



umbones are very slightly bent forward, and are situated at about the anterior 

 third ; left valve with about thirty low, flat radial ribs, becoming wider and 

 sparser posteriorly, crossed by rather rude incremental lines, but not nodulous 

 or dichotomous, and with subequal, rather shallow channelled interspaces ; 

 the right valve is similarly sculptured and somewhat smaller; cardinal area 

 rather long, narrow, with numerous slightly angular, longitudinal grooves ; 

 ends of the hinge-line moderately angular, anterior end of shell rounded, 

 posterior produced, base flexuous, inner margins fluted; teeth numerous, 

 small, uninterrupted, nearly vertical, the distal ones larger and tending to 

 break up into granules. Lon. of a large valve 50, alt. 34 mm. ; of figured 

 specimen, lon. 38, alt. 27, diam. 20 mm. 



This species is one of the most abundant in the Floridian Pliocene, and 

 is easily distinguished from any other by its compressed appearance and 

 twisted shape. Some of the allied species have a slight flexuosity, but in 

 none is this feature so pronounced as in A. cainpyla. A variety with thinner 

 shell and narrower and slightly more elevated ribs was at first thought to be 

 distinct, and may be named var. cBvctea. It is figured plate 32, figure 22. 



Scapharca (Scapharca) subsinuata Conrad. 

 Area subsitiuata Conrad, Fos. Med. Tert., p. 62, pi. 32, fig. 6, 1S45. 



Pliocene of the Croatan beds, near New Berne, North Carolina. 



I have seen only one specimen of this shell, which was identified by 

 Conrad and has been many years in the National collection. It is verj' close 

 to A. arata Say, from which the individual referred to differs chiefly by having 

 two or three more ribs, and in being somewhat less angular at the posterior 

 end of the hinge-line. A good series would probably connect them. 



A species near to this is represented in the Upper Miocene fauna of the 

 deep artesian well at Galveston, Texas, but the specimens are too young to 

 be specifically identified. 



Scapharca (Scapharca) transversa Say. 



Area transversa Say, Journ. Acad. Nat. Sci. Phila., ist Ser., ii., p. 169, 1822; Conrad, 



Fos. Tert. Form., p. 15, pi. I, fig. 2, 1832; Tuomey and Holmes, Pleioc. Fos. S. 



Car., p. 42, pi. 15, fig. 6, 7, 1856 ; Emmons, Rep. Geol. N. Car., p. 285, 1858. 



Pliocene of Myakka River and De Land, Florida; Pleistocene of North 



Creek, Little Sarasota Bay, Florida; of Simmons Bluff, South Carolina, 



Wailes Bluff, Maryland, and Sconset, Rhode Island. Recent from Cape Cod 



