134 SYSTEMATIC PALEONTOLOGY 



Family TORNATINID/E. 



Genus VOLVULA Adams. 



VOLVULA IOTA (Conrad). 



Plate XXXIX, Figs. 6, 7, 8, 9. 



Bulla acuminata Conrad, 1830, Jour. Acad. Nat. Sci. Phila., toL vi, 1st ser., p. 210. 

 Bulla acuminata Conrad, 1842, Proc. Nat. Inst., BuH. ii, p. 186. 

 Ovula iota Conrad, 1843, Proc. Acad. Nat. Sci. Phila., vol. i, p. 309. 

 Amphiceras iota Conrad, 1854, Proc. Acad. Nat. Sci. Phila., vol. vii, p. 31. 

 Volvula iota ? Harris, 1893, Amer. Jour. Sci., ser. iii, vol. xlv, p. 24. 

 Not Volvula acuminata Sowerby. 



Description. — " Narrow-elliptical, with minute spiral lines towards the 

 base ; inner margin regularly arched above the middle of the shell, where 

 the aperture is very narrow, widening a little towards the apex ; aperture 

 gradually expanding from the middle to the base; labrum very slightly 

 rounded; labium reflected. Length, quarter of an inch." Conrad, 1843. 



There are four varieties of Volvula in the Miocene of Maryland, 

 some or all of which may be entitled to specific rank. It is very doubtful 

 to which of these varieties Conrad intended the name iota to be applied. 

 The original specimens came from Plum Point. 



Volvula iota var. makylandica n. var. 

 Plate XXXIX, Fig. 6. 



This is the form which Conrad referred to acuminata. It differs from 

 the acuminata of the European authors in lacking a columella fold, and 

 in being less elongate. It is distinguished from our other varieties by 

 its sharp spire. 



Length, 2.5 mm. ; diameter, 1 mm. 



Occurrence. — St. Mary's Formation. St. Mary's River, Cove Point, 

 Langiey's Bluff. Choptank Formation. Paw Paw Point. Calvert 

 Formation. Plum Point. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. Xational Museum. 



A^olvula iota var. diminuta n. var. 

 Plate XXXIX, Fig. 7. 

 This form is long and slender and has a 1)lunt spire. It is cylindrical 

 and of nearly uniform diameter. It is to this form that Conrad applied 

 the catalogue name '"' diminuta." 



