lyy Midway Stage ^3 



CRASSATELLA. 

 Crassatella gabbi, PI- 5, figs. 7, a, 8, 9 10, n- 



Syn. C. pteropsis Gabb, ^z^^z Con., Jr. Ac. Nat. Sci., Phila., 

 vol. iv, i860, p. 395. pl- 68, fig. 28. 

 C. gabbi Safford, Am. Jr. Sci., II, vol. xxxvii, p. 368, 



1864. . , ^ , .. 



Crassatella sp. Harris, Geol. Surv. Ark., 1892, vol. 11, 



p. 43. 

 C. tumidula Aid., Geol. Surv. Ala., 1894, p. 242. 



Gabb's original flr^.ym>//^«.— " Subtriangular, flattened; beaks 

 very small; in some specimens a slight depression m advance ot 

 the umbonal ridge, which is rounded; surface marked by heavy 

 transverse ribs, which become faint on and behmd the umbonal 

 ridge- hinge rather small; muscular scars deeply impressed; cardi- 

 nal Margin straight, anterior margin regularly rounded, basal 

 margin slightly sinuous, posterior subangular. 



^^ Dimensions. —l^^g'C^. .gin., width, 1.4m., height of valve, 



■^ '^^^^/z/y.— Ripley group, Hardeman Co., Tenn., Prof. Safford; 

 and from the same formation at Eufala, Ala. Collection of the 

 Smithsonian Institution, No. 553." 



Gabb's description answers fairly well to the type specimen in 

 Dr. Safford's collection, a figure of which is herewith given. 



His "dimensions," however, were evidently taken trom tiie 



Smithsonian specimen. ^^ j. • f^^ 



Since Conrad had previously proposed the name pteropsis iox 

 a species of Crassatella, it was eminently proper for Dr. battord 

 to rename this species in Gabb's honor. . • ^1, 



Several years ago the writer encountered this species in the 

 Midway of Arkansas, and from the great variety of forms it pre- 

 sented, supposed that there were two species. However none 

 were well enough preserved to admit of positive identification or 

 clear description, hence they were passed by un-named. 



In Texas one of the same forms has been found in the Mid- 

 way on Brazos river. A manuscript name was proposed but 

 the description was never printed. The figure of that form is 

 given on pi. 5, figs. 10, n. , 



If all the specimens in hand at present really represent but 

 one species, as seems most likely, it presents a remarkable 

 amount of, variation in shape and surface markings. In the 

 type specimen and all specimens from near Middleton sent here 

 by Dr Safford, there are a dozen or more strong concentric tolds 

 on the medial and anterior portion of the valve, but posteriorly, 



