100 BULLETIN &0, UNITED STATES NATIONAL MUSEUM. 



TURRITELLA ATACTA, new species. 



Plate 13, fig. 5 ; plate 14, fig. 5. 



TurriteUa gatunensis Dall, Trans. Wagner Inst., vol. 3, pt. 2, p. 310, pi. 

 17, fig. 10, 1S92, not of Conrad. 



This species resembles rather closely Conrad's description of T. 

 uvasana (but not his figure, which is a mere caricature) and the 

 Costa Rica species recently named tristis by Brown and Pilsbry, 

 which was figured by Gabb in 1878, under the name of gatunensis. 

 A careful review of the available material leads to the belief that it 

 is distinct from either. Any one who will compare either of Gabb's 

 figures with the original diagnosis of T. uvasana will certainly find 

 them irreconcilable. The figure on plate 13 represents what may be 

 a variety. 



The shell is slender (13 whorls to 26 mm.) with a rather indistinct 

 suture. The top of the whorls flattish or slightly excavated with 3 

 or 4 medium spiral threads with a much finer thread in the inter- 

 si^aces; the rest of the whorl with 3 prominent major threads, equi- 

 distant and with 2 or 3 smaller threads in the intervals; the base 

 slightly' convex with 1 major and numerous minor spiral threads; 

 aperture subquadrate, the outer lip somewhat flexuous; length of 

 type-specimen (13 whorls) 26 mm., breadth 6 mm. 

 • Tampa silex beds at Ballast Point, Tampa Bay, Florida. U. S. 

 Nat. Mus. No. 165123. 



The shell figured as T. uvasana by Gabb in the Paleontology of 

 California has rather prominently rounded whorls with 5 or more 

 subequal, equally distributed spiral threads, and there is a Califor- 

 nian species with these characters, but the diagnosis of T. uvasana 

 calls for quite different characters. T. gatunensis Conrad has been 

 shown by Pilsbry to be quite distinct. The tristis of Pilsbry and 

 Brown should be carefully compared with uvasana Gabb not Conrad. 

 T. atacta belongs in the group with T. acropora Dall of the Plio- 



cene. 



Family VIVIPAEIDAE. 



Genus LIOPLAX TroscheL 



Lioplax Troschel, Gebiss d. Schneckeu, vol. 1, p. 100, 1857. Type, Palu- 

 dina subcarinata Say. 



LIOPLAX FLORIDANA Dall. 



Plate 16, fig. 8. 



Lioplax floridana Dall, Trans. Wagner Inst., vol. 3, pt. 1, pi. 1, fig. 3, 

 1890. 



Tampa silex beds at Ballast Point, Tampa Bay, Florida. U. S. 

 Nat. Mus. No. 111937. 



