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657 



TERTIARY FAUNA OF FLORIDA 



distally much wider, and more or less oblique ; interior margin of the valves 

 with strong, short flutings. Lon. 47, alt. 28, diam. 27 mm. 



This is quite a peculiar species, the teeth of which recall Argina, while 

 all the other characters of the shell indicate its section to be Anadani, another 

 instance, if one were needed, to illustrate the mutability of the dental forms 

 in this family. It cannot be confounded with any of our other species. 



Scapharca (Anadara) clisea n. s. 

 PLATE 33, FIGURE 25. 



Chesapeake Miocene of Maryland, at St. Mary's River and Crisfield ; of 

 Nomini Cliffs, Virginia, Harris; and of Walton County, Florida, Johnson. 



Shell large, heavy, inflated, short, with small, high, somewhat prosocce- 

 lous beaks, the two halves of the wide cardinal area inclined to one another 

 in the adult at an angle of about forty-five degrees ; left valve with about thirty 

 strong, flattened subequal radial ribs with narrower interspaces ; in the young 

 the ribs are furnished with small transverse nodulations, which gradually 

 become obscure in the adult; the only transverse sculpture is of the ordinary 

 incremental lines; the ribs in the adult are flat topped and rarely show any 

 tendency to mesial sulcation, and when present it appears only on a few of 

 the anterior ribs near the margin ; the anterior end is obliquely rounded to 

 the base, the posterior end a little produced basally; the cardinal area is 

 exceptionally wide, with a single impressed line joining the beaks and six or 

 seven concentric lozenges defined by sharp grooves ; a deep groove also 

 bounds the area ; hinge-line straight with numerous small vertical teeth, 

 becoming much larger distally and tending to break up into granules at both 

 ends of the series in the senile shell. Lon. 51, alt. 53, diam. 53 mm. 



This shell is apparently related to A. ralliplcnm and A. stanriiica Conrad, 

 and a larger scries of specimens may oblige us to unite all three as varieties 

 of a single species. At present, however, the differences seem too great to 

 admit of this course. In A. callipUiira the ribs are granulated and triply 

 suleate, while in the present form they are simple. . /. clisea has no posterior 

 truncation like that figured by Conrad in A. calliplcitra. A. staminca is more 

 squarely compressed before and behind, with a tendency to incurvation of the 

 posterior basal margin; it is a smaller shell with more posterior beaks, and 

 less roundly inflated. We have a large series of this species from many 

 localities, and these differences characterize them all. The forms are easily 

 differentiated, so far as our present knowledge goes, and therefore are better 



