204 SYSTEMATIC PALEOXTOLOGY 



Family TEREBRATULIDAE. 



Genus TEREBRATULA Llhwyd. 



Teeebeatula haelaxi Morton. 



Plate LYIII, Figs. 3, 3, 3a. 



Terebralida Tiarlani Morton, 1829, Jour. Acad. Nat. Sci. Phila., vol. vi, p. 73, pi. 



iii, tigs. 1-4, 7, 8; Amer. Jour. Sci., vol. xvii, p. 283.; vol. xviii, pi. iii, tig. 



16. 

 Terehrntula harlani Baii-g, 1898, Amer. Geol., vol. xxii, p. 370. 



Description. — " Shell large, about twice as long as broad, sides straight 

 and imiDerfectly parallel; npper yalve plano-convex, obscurely bipli- 

 cated except near the margin, which has three inconsiderable sinnses; 

 lower valve very convex, with a longitudinal ridge and slight lateral 

 depressions; beak incurved; umbo prominent." Morton, 1829. 



Mr. Schiichert states in a private communication that " The Tere- 

 hratiila liarlani from the Eocene show a tendency to variation which if 

 constant I would use as, a distinguishing character for the establishing 

 of a variety. This tendency is for the shell to become a little wider with 

 the loss of lobation. Similar shells also occur among the Cretaceous 

 specimens but the form seems to be rare. If in the Eocene this form 

 is the prevailing one then it shows the line of variation in evolution. 

 However, if you give these Eocene specimens a varietal name, call atten- 

 tion to the fact that the identification cannot be made from single 

 specimens. 



" Another slight difference is the wide area on each side of the crural 

 processes. This also has no particular value. I should never have be- 

 lieved the finding of Terehratula liarlani in Eocene strata had I not 

 seen these specimens with your remarks as to occurrence and associated 

 Eocene fossils." 



Whether the specimens of Terehratula harlani found associated with 

 typical Eocene fossils are to be regarded as mechanically derived from 

 Cretaceous deposits or are really Eocene representatives of this import- 

 ant species the authors have not been able to determine. A careful 

 study of the many shells found does not afford any evidence that they 

 were transported to any distance although in some instances occurring 

 well above the base of the Eocene. Furthermore, it cannot be definitely 



