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653 



TERTIARY FAUNA OF FLORIDA 



feet. For the formation in which it occurs, and which is clearly distinct from 

 any yet described from middle America, Spencer has proposed the name of 

 the Coatzocoalcos formation, from the Coatzocoalcos River, which drains the 

 coastal plain immediately to the eastward. The species is named in honor 

 of Dr. Spencer, who collected it. 



Scapharca (Bathyarca) Hendersoni n. s. 

 PLATE 33, FIGURE 9. 



Oligocene of the Bowden beds, Bowden, Jamaica, where it was collected 

 by J. B. Henderson, Jr., and Mr. Charles T. Simpson. 



Shell very small, much inflated, the hinge-line as long as the shell, which 

 is of a rounded triangular form, with rather prominent prosoccelous beaks ; left 

 valve with fine, elevated, rounded concentric lines, crossed by closer, less promi- 

 nent, and finer radial lines ; in the right valve, as usual in this section of the 

 genus, the radial sculpture predominates over the concentric, the latter though 

 present being inconspicuous ; cardinal area moderately wide, the beaks being 

 nearly medial, the surface of the area longitudinally striated ; hinge with about 

 five nearly vertical anterior teeth separated by a wide unarmed gap from six 

 or seven smaller, more oblique posterior teeth ; margin of the valves thin, 

 entire, or microscopically crenulated ; the inner edges of the adductor scars 

 slightly raised above the inner surface of the valve. Lon. 2, alt. 2, diam. 2 mm. 



This minute little species is obviously adult, and about ten valves were 

 obtained. It resembles A. pcctunciiloides Scacchi and A. glomcrula Dall, of 

 the recent fauna, but is smaller, more inflated, and more triangular than either 

 of them. It is named in honor of Mr. Henderson, during whose explorations 

 in Jamaica it was collected. 



Another species of the same group with more conspicuous radial 

 sculpture and a marked depression radiating mesially from the beaks was 

 obtained by Professor R. T. Hill from the Oligocene of Monkey Hill, on the 

 line of the Panama Railway, but the two valves obtained are hardly perfect 



enough for description. 



Section Anadara Clray. 

 Scapharca (Anadara) rustica Tuomcy and Holmes. 



Pi, ATE 31, FIGURES 6, 9. 



nistii-a Tuomey and Holmes, Pleioc. Kos. S. Car., p. 29, pi. n, figs. 6-10, 1857. 

 Nut ./. nislii-tj C'ontejcan, 1859. 



Ann <r<;/( v/w Hcilprin, Trans. Wagner Inst., i., p. 96, pi. 13, fig. 30, 1887; Dana, 

 Man. (ieol., 4th cd., p. 900, fig. 1508, 1895. 



