Bulletin 31 18 



imens of this species are common at Hamilton Bluff, Ala. 

 Anomia naviceliodies var. hammetti Har., PI. 12. Figs, i, 2 



l^arietal diaraderization. — Shell long-ovoid as illustrated; 

 rather thick, ver}- flat, somewhat curved ; exterior marked b}' a 

 large number of irregularly divaricating, radiate riblets having a 

 tendency to develop minute, hollow prickles ; broad, concentric 

 undulations irregularly disposed. 



Along with this upper left valve there are fragments of 

 heavy right valves, shown on pi. 11, figures 4 and 5 that in all 

 probabilit}' belong to this species, though we have not thus far 

 found two valves together to prove the question bej'ond a doubt . 

 These show a remarkable thickening about the opening as well 

 as about the whole cardinal area. 



Type. — Deposited in Pal. Mus., C. U. 



Horizon.— '^t. Maurice Eocene. 



Specimens figii7-ed. — From Hammett's Branch, I. a. 



Localities. — Hammett's Branch and Bayou Negreet, La. 



Plicatula filamentosa Con., PL 12, fig. 3, et. seq. 



vSee Bull. Am. Pal. vol. 2, p. 233. h\^o P. filamentosa Dall, Trans. 

 Wag. &c., '98, p. 762. 



The appearance of radii within young shells and their grad- 

 ual obscuring by calcareous thickening within is well shown b>- 

 figures4, 5 and 6. De Gregorio (Eoc. Faun. Ala., p. 179) has 

 described a 3^oung valve like fig. 4 as ''Spondylus amussiopse.^' 

 Exteriorly just outside the irregular attachment area, faint radi- 

 ating plications appear in young forms, especially of the upper 

 Sabine horizon. Next, strongly marked concentric lines of 

 growth at certain regular intervals giving the appearance of fim- 

 briate radiating lines ; fourthly, deep radial folding, often mainl}- 

 sub-marginal. The Sabine forms have more regular and numer- 

 ous plications than the later specimens of this species. But the 

 concentric lines with the tendency to produce ribs of a second or- 

 der is already noticeable in a few specimens from Hatchetigbee. 



Typical ^/aine?itosa must be regarded as the Claiborne form, 

 shown by figs 3-8. A comparativel)' small number of plications, 



