MUSEUM OF COMPARATIVE ZOOLOGY. 163 



Subgenus CONOMITRA Conrad. 

 ? Conomitra Conrad, Am. Journ. Conch., I. p. 25, 1865. 



Shell stout, short, like a short Beta; spire obtuse with a relatively large 

 shelly mammillate nucleus ; outer lip straight, simple, smooth inside ; colu- 

 mella nearly straight with 3-5 rather strong plaits enlarging backward; no 

 posterior notch ; siphonal notch deep ; surface smooth or axially plicate or 

 reticulated. 



This group resembles Microvoluta Angas, but in that the siphonal notch 

 is wanting or obsolete, and the general form more elongated ; in Strigatella 

 and Zierliana the outer lip is armed, and the dentition of the columella is 

 quite different. It differs from the type of Conomitra Conrad in its apex, in 

 its simple outer lip, and in the absence of the peculiar anterior attenuation. 

 I have not been able to find any other group into which it would fit in a 

 satisfactory manner, and have decided to use Conrad's undescribed name for 

 it ; I do not feel positive that it really belongs in the Mitrida*, yet its form, 

 plaits, and nucleus seem more allied to such forms as M. Hanleyi Dohrn than 

 to Enceta and the other connections of Voluta. The colors are exactly those 

 of Enceta. It is possible that there may be a caducous nucleus, and that the 

 mammillary tip is merely the consolidated base thereof ; this cannot be deter- 

 mined until quite young specimens have been obtained. My impression is, 

 however, that the apex is naturally mammillate, as in Mitra Hanleyi. The 

 species like M. (?) styria have an elongated rather acute translucent nucleus of 

 three or four whorls, like a little Assiminea, which is usually lost. This may 

 be a character of Turricula. 



The type of Conomitra Conrad, on which, in default of any diagnosis, the 

 subgenus must rest, is Mitra fusoides Lea (Contr. to Geol., p. 169, t. vi. fig. 176, 

 1833). C. staminea and C. vicksburgensis Conrad, the latter being unfigurecl, 

 are probably mere varieties of Lea's shell, which was derived from the Clai- 

 borne beds. The differences between them are such as I observe between my 

 specimens of C. Blaheana. The simple unlirate outer lip of the latter may be 

 due to the period of growth; at all events. I prefer to retain the recent form 

 with Conomitra until there is more material available upon which to base a 

 final decision. This is the more desirable since the Miocene C. angulata Heil- 

 prin, from the Tampa silex beds, with the smooth outer lip of the recent form 

 has the small pointed apex of the Eocene type. 



Conomitra Blakeana n. s. 



Shell columbelliform, short, stout, the aperture equalling or exceeding half 

 the shell ; apex large for the shell, mammillate ; whorls about six, their pos- 

 terior faces well rounded and somewhat turrited between the sutures ; the 

 elevation of the spire different in different specimens ; sculpture of numerous 

 close stout transverse ribs with very narrow interspaces, incremental lines 



