INSTITUTE OF SCIENCE, PHILADELPHIA. 367 



Natica (Oryptonatica) pusilla Say. 



Nalica pusilla Say, Journ. Acad. Nat. Sci. Phila. ii. p. 257, 1822 ; Dall, Bull. 37 U. S. Nat. 

 Mus., p. 154, pi. 50, fig. 21, 1889. 



Pliocene of the Caloosahatchie and Shell Creek, Florida, Dall and Will- 

 cox ; Post-Pliocene of Simmons's Bluff, S. C, Burns ; living on the coast of 

 the United States from Massachusetts to the Florida Keys and westward to 

 Texas, in 2 to 15 fathoins. 



This pretty little species may perhaps be regarded as a recent analogue 

 of N, floridana, which it much resembles, but on a much smaller scale. 



Genus POLYNIOES Montfort. 

 Polynices Montf., Conch, ii. p. 223, 1810 ; type N. mammilla Lin. 



This group in its widest sense is here taken as including all the Naticidce 

 with corneous opercula. It is divisible into several subgenera based on the 

 form of the shell. 



Polynices s. s. will include the simply colored mainmiform species with a 

 smooth surface and the umbilicus usually solidly filled with callus. 



Naticina Guilding {iion Fischer) is a synonym, though the name has been 

 wrongly applied to the Naticiform Sigareti called Eiinaticina by Fischer and 

 Sigatica by Meyer. 



Neverita includes the large, rather depressed forms usually grouped 

 under this name. 



Lunatia Gray includes the thin, globose species with a small umbilicus 

 indistinctly or not at all ribbed internally, and a small callus on the pillar or 

 none. 



Mamuiilla Schumacher includes the forms resembling Polynices s. s. in 

 form, but with thinner shells, a partially open umbilicus, and, in life, a con- 

 spicuous epidermis. 



Payraudeantia B. D. & D. has the umbilicus of Natica s. s,, doubly 

 ribbed and excavated, but a horny operculum. 



Ampullina (Lam.) Bowdich, 1822, covers the singular Eocene forrns in 

 which the umbilical carina is sharp, and in the section Ampiillinopsis Con- 

 rad, 1865 i^MegatyloUis Fischer), has an elevated spire with a channelled suture ; 

 in Cei'nina Gray has the spire depressed, the suture simple, and the umbilical 

 region hidden in a profuse callus ; both these have a smooth surface, while 

 Lacunaria Conrad has an elevated, sharp spire, a narrow umbilicus, not callosi- 

 fied, and a thin, sometimes sculptured shell. Type N. a/rt(5«;«zV«5W Whitfield. 



Aviauropsis Morch has a thin, nearly or quite imperforate shell with a 

 channelled suture; it is probably not nearly related to Amaura MoUer. 



There are a number of other groups not represented in our Tertiary, and 

 which it is not necessary to refer to at present. 



Subgenus Neverita Risso. 

 This group is represented in the Eocene by N.gibbosa Lea, with which 



