126 THE XAUTILUS. 



h. Ril)lets granular or venuiculate. 

 D. texasiana Phil. Small, shape of variabilis. Galveston to Vera 

 Cruz. 



2. Posterior end more rounded, sculpture feeble. 



a. Shell compressed. 



D. fossor Say. Olive uith blue rays. New Jersey to INIayport, 



Florida. 

 D. incerata Hanley. Small, subovate, very flat. Extra-limital, 



Bahamas. 



b. Shell inflated. 



D. tumida Phil. Small, vezy stout, jjolished. St. Augustine to 

 Texas and Vera Cruz, Mexico. 



IpHiGEKiA Schumacher. 



J. brasiliaiia Lam. Lateral teeth obsolete. Indian River, Florida 



south to Kio Janeiro. 



Donax protradits Conrad is an extremely large and senile speci- 

 men of D. fossor. D. variabilis presents similar modifications when 

 very old, becoming abnormally long and arcuate. D. jxirvtda Phil., 

 is the very young D. fossor. D. Lamarckii Desh., is identical with D. 

 striata Linne. D. angxistatiis Sow. is a well-grown D. fossor, not 

 quite so old as the type of protradus, D. elougatns Sow. and Han- 

 leyana Phil, (^fide Sow.) equal rugosa Linne, non Sow. The writer 

 has received adventitious specimens of D. californica Conr., D. navi- 

 cula Rve. and D. pundostrtatus Hani, from Florida, as indigenous 

 to that coast. The following species are known in the fossil state 

 from the eastern United States : D. idonea Conrad is supposed to 

 be INIioceue and was described from a valve cast up on the coast of 

 North Carolina and supposed to be from a submarine bed of fossils; 

 D. emmonsii Dall (Emmons Geol. N. C. p. 298, fig. 227 which has 

 been misplaced in the text) from the later tertiaries of Cape Fear 

 River ; D. cequilibrata Dall, same locality, collected by Mr. C. W. 

 Johnson ; D. fossor Say occurs in the Pliocene of Florida and South 

 Carolina ; D. variabilis in the Pleistocene of South Carolina. The 

 Miocene references to these two forms are in need of confirmation 

 and the variabilis of the Pliocene of Tuomey and Holmes is D. 

 fossor. The Eocene forms referred by Conrad to the genus Egeria 

 are doubtfully related to Dondx. D. wqiiilibrata may be briefly 

 characterized as follows: shell longer in proportion to its height 

 than in any of our recent species, rounded in front, the posterior 



