94 TRANSACTIONS OF THE WAGNER FREE 



was worn before it was fossilized, so that the absence of the transverse stria- 

 tion, called for by the diagnosis of mississippiensis and absent on our fossil, is 

 not significant. 



Our shell is elegantly fusiform, slender, with gently rounded whorls, ap- 

 pressed suture and faint incremental lines, or none ; sculpture of sharp-edged, 

 revolving ridges, four between the sutures, and on the last whorl an intercalary 

 smaller thread ; there are fourteen or fifteen nearly uniform primary ridges on 

 the last whorl. Lon. of last whorl 23.2; of aperture 17.O; max. lat. of whorl 

 9.5 mm. 



Tampa silex-beds, between Ballast Point and the town ; Mr. Shepard. 



This shell is related to such species as M. striatida Lamarck, by its sculpt- 

 ure, and still more to such species as M. pia Dohrn and M. Hindsii Reeve, of 

 West America. I doubt its pertinence to M. mississippiensis Conrad, but the 

 differences may be due to age, wear and imperfection of the specimen. 



This species and those which precede it, except M. carolinensis, would 

 have been included in Conrad's genus Fusiviitra, of which M. celbdifera Con- 

 rad was the first species. But this genus never had any value, and Conrad's 

 original list contained the precursors of species as different as M. wandoensis 

 and M. Sivainsoni Brod. 



There are several closely allied forms in the Eocene, one of which almost 

 unchanged has come down to us living in the deep water of the Gulf of 

 Mexico. 



Mitra conquisita Conrad, is a common species of the Upper Eocene with 

 which a shell named and figured from the Jackson beds by Conrad in Wailes' 

 Geology of Mississippi as M. MiUingtoni (but never described) was afterward 

 confused by Conrad himself The former is a much smaller and proportion- 

 ally stouter shell, M. MiUingtoni is found up to 130 mm. in length, and is 

 the precursor of M. Swainsoni Broderip (West America) and the form which 

 in my report on the Blake Gastropods I have called M. Swainsoni var. Antil- 

 lensis. From the latter the fossil is not separated by any specific characters 

 of serious importance. Internal casts of it were found in the soft limestones 

 at Ocala. 



Gabb's Miocene Mitra Titan from Santo Domingo appears to be almost 

 identical with M. MiUingtoni. 



Subgenus Conomitra Conrad. 

 Conomitra staminea Conrad. 

 Plate 4, figure 2. 

 Mitra slaminea Conrad, Journ. Acad. Nat. Sci. 2, vol. i. p. 120, pi. 12, fig. 4, Aug. 1848. 

 M. vicksbiirgensis Conrad, op. cit. p. 120. 

 Conomitra angnlata Heilprin, Trans. Wagner Inst. i. p. no, pi. 15, fig. 47, 1887. 



Upper Eocene at Vicksburg, Miss. ; Lower Miocene at Ballast Point, 

 Tampa Bay, at Six-Mile Run, near Orient Station, N. E. from Tampa, and at 



