364 TRANSACTIONS OF THE WAGNER FREE 



Subgenus Natica s. s. 

 Natica canrena (Linn^) Morch. 



Nerita canrena l^mxii. pars) Auct., Morch, Malak. Blatt. 24, p. 62, 1877. 



Natica canrena Tuomey and Holmes, Pleioc. Fos. S. C, p. 115, pi. 25, fig. 17, 1857 ; Em- 

 mons, Gaol. N. C, p. 267, fig. 152, 1858. 



Natica plicatella Conrad, Proc. Acad. Nat. Sci. Phila. 1862, p. 564, 1863; Am. Journ. 

 Conch, iii. p. 259, pi. 24, f. 3, 1867. 



Older Miocene of Santo Domingo, of Bowden, Jamaica, and the Chipola 

 beds, N. W. Florida ; Newer Miocene of North Carolina, at Wilmington ; 

 Pliocene of Costa Rica, Gabb, and of the Caloosahatchie, Shell Creek, Alli- 

 gator Creek, etc., Florida, Dall and WiUcox; living from Cape Hatteras 

 southward on the coasts of the United States and the Antilles and of South 

 America to Pernambuco. 



Hanley has shown that the canrena of Linne was a compound of several 

 different species, and that which later authors have generally accepted as the 

 true canrena is that figured by Lister. Deshayes would reject the name can- 

 rena altogether on account of this confusion, but it is doubtful if this would 

 be allowable. The East Indian s'^ecits,N.ala-papilio7iis,\s the one most com- 

 monly confounded with the American form, and it is figured under the name 

 of canrena in the excellent manual of Dr. Fischer (PI. viii. f i). If the 

 name canrena should be retained for the Asiatic species, which has a different 

 operculum from the American shell, the earliest name for the latter seems to 

 be pellis-erminea of Martyn. 



Conrad proposed for the Miocene fossil the name of N. plicatella, which 

 may be used in a varietal sense to cover the older Miocene forms, in which, 

 though the shells are absolutely identical, the operculum differs slightly from 

 that of the newer Miocene, Pliocene and recent shells. The latter has about 

 ten channelled, deep grooves, separating as many flattened, subequal ribs, 

 which become narrower and more keeled toward the outer margin of the 

 operculum. The central portion of the latter has an irregular, little-elevated, 

 callous area. In the operculum of the variety plicatella, as here restricted, 

 the central callus is more elevated, with its margin limited by a conspicuous 

 groove, while another similar groove separates the outermost rib from those 

 inside from it. This character may not be constant, but until this is shown 

 it would seem advisable to retain the varietal name, notwithstanding the 

 shells offer no differential characters. We have a somewhat similar case in 

 the recent Fasciolai-ia princeps of California and F. gigantea Kiener of 

 Florida. The shells cannot be differentiated, but the opercula are markedly 

 unlike. 



The Eocene precursor of this type seems to be Natica semilnnata Lea, 

 of which N. minor Lea is merely a young and elevated specimen. In this 

 species the young has the umbilical rib very distinct, but in completely adult 

 specimens the rib has frequently become so obsolete as to have practically 



