196 SYSTEMATIC PALEONTOLOGY 



end; labrum sometimes lirate: body whorl with eighteen longitudinal 

 ribs terminating in a subsutural row of tubercles, and with about sixteen 

 sharply impressed spiral lines with much broader interspaces, the spiral 

 lines (except the subsutural one) not crossing the longitudinal ribs ; spire 

 regularly pyramidal. 



This species most closely resembles N. peralta, of which it is probably 

 the ancestor. It differs from it in being much smaller, in having a less 

 expanded mouth, and in not having the longitudinal ribs crossed l)y the 

 spiral lines. 



Length, 11 mm,; diameter, 5.5 mm. 



Occurrence. — Choptank Formation. Jones Wharf, Governor Kun 

 (lower bed), Greensboro, Trappe Landing. Calvert Formation. Plum 

 Point, Church Hill, Fairhaven. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 Cornell L^niversity, U. S. National Museum. 



Nassa trivittata Say. 

 Plate XLIX, Fig. 12. 



Ifassa Irivittata Say, 18"^3, Jour. Acad. Nat. Sci. Phila, vol. ii, 1st ser., p. 281. 



This species has been repeatedly listed from the Miocene of Maryland, 

 but it has been supposed that in every case it was a misdetermination of 

 Nassa peralta Conrad. The Johns Hopkins collection contains 8 un- 

 doubted specimens of this species which were in a tray of N. peralta from 

 St. Mary's river. Probably they came from the Pleistocene at Cornfield 

 Harbor (where they occur abundantly), and were mixed with the Mio- 

 cene specimens by accident. Several quarts of specimens of N. peralta 

 collected by the Maryland Geological Survey and by the Cornell and 

 Wagner Institute expeditions have been carefully searched without find- 

 ing a single specimen of N. trivitatta. In all probability the species is 

 entirely post-Miocene. It is hoped that future collectors will give this 

 question their careful attention. 



Occurrence. — St. Mary's Formation (?). St. Mary's Eiver (?). 



Collection. — Johns Hopkins University. 



