86 BULLKTIN II 86 



ferred to the same depends on the verdidl of paleontologists after 

 better material than I have j^et seen from that locality is ob- 

 tained. Dall says: 



"Since this group remounts in the geological scale to the De- 

 vonian, it is not so extraordinary that one of the species should 

 persist from the uppermost Cretaceous to the present day. No 

 differential characfters have ever been recorded which would sep- 

 arate Morton's shell from the Eocene form which follows it, and 

 I can assert with confidence that the latter cannot be discrimin- 

 ated from the Miocene and recent forms by any constant charac- 

 ters. If this succession be admitted, it is a strong testimony to 

 the protecftive value of the device by which the members of this 

 family defend themselves." 



Lignitic locality. — Ala. : Woods bluff. 



Specimen figured. — Paleontological Museum, Cornell Univer- 

 sity. 



Natica semilunata, PI. ii, fig's. 18-20. 



Syn. N. semilunata Lea, Cont. to Geol., 1833, p. 108, pi. 4, fig. 93. 

 f N. perspeEla Aid., Geol. Geol. Surv. Ala., Bull, i, p. 56. 

 N. epiglottina, et at. of de Greg., Mon. Faun. Eoc. Ala., p. 148, etc. 

 N. minor Coss., Ann. de Geol. et de Pal., 1893, p. 25. 

 N. semilunata Coss., Ann. de Geol. et de Pal., 1893, p. 25. 

 N. semilunata Dall, Trans. Wag., etc., vol. 3, p. 364. 



Lea's original description. — "Shell subglobose, smooth; sub- 

 stance of the shell rather thin; spire slightly elevated; suture 

 rather impressed; columella but slightly thickened, the callus 

 being reflecfted at the middle of the umbilicus; umbilicus large 

 and grooved; whorls five, inflated, slightly flattened below the 

 suture; mouth semi-lunate, about two-thirds the length of the 

 .shell. Length .4, breadth 7-20 of an inch." From Claiborne, 

 Ala. 



The Lignitic beds offer greater varieties of this species than 

 the Claiborne sand does. Dall is doubtless right when he says: 

 "In this species the young has the umbilical rib very distin(5l, 

 but in completely adult specimens the rib has frequently become 

 so obsolete as to have pracftically vanished. " A large and prob- 

 ably more or less diseased form is shown by fig. 19, which still 

 retains a very sharply defined and large umbilical rib. This, 

 however, is a rare exception. 



