438 TRANSACTIONS OF THK WAGNER FREE 



a broken fragment from either part of the shell can rarely be relied upon ta 

 give differential characters for the species as a whole. In the same species, 

 among the sculptured ones a good deal of variation in the strength of the 

 sculpture between different specimens is extremely common, and should always 

 be allowed for. 



Genus DENTALIUM Linn^. 



In the Eocene of Claiborne, the horizon of the ferruginous sands affords 

 five species of Dentalmm which are well characterized. These are D. thalloide 

 Conrad {alternatum Lea), D. arciforme Conrad (Z?. Leai Meyer), D. blandnm 

 De Gregorio, and D. mitmtistriatiim Gabb {D. anmilatum Meyer). D. blati- 

 diini is shorter, smaller, thinner, with finer and less prominent sculpture than 

 D. alternatum. D. arciforme Conrad is smooth, but toward the posterior end 

 is sometimes microscopically longitudinally striated for a short distance. The 

 posterior orifice is originally circular, subsequently with a wide sulcus dorsally 

 and ventrally; when truncate and repaired it has a curious bilabiate supple- 

 mentary inner margin which has been figured by Meyer. D. minutistriatiun 

 Gabb usually occurs in fragments, which are more slender and straighter than 

 similar pieces of D. arciforme. The Texas specimens of inimitistriatum are 

 sometimes more sharply striated than the Claiborne shells, and those from the 

 older Eocene Prairie Creek beds are more distinctly annulate. But these differ- 

 ences merge into one another even in the same locality. The species is found 

 in the Prairie Creek beds, on the Sepulga River, and other places in Alabama, 

 and Lee County, Te.xas. Another nearly smooth species from the Eocene of 

 Alabama, Mississippi, Louisiana and Texas is D. tnicrostria Heilprin. D. 

 himixttun De Gregorio is probably a fragment of it. D. thalloide Conrad (Z>. 

 alternatum Lea) is very common in the Claibornian at Claiborne, near Clarks- 

 ville and Wood's Bluff, Alabama, Wahtubbee and Newton, Miss., and Creole 

 Bluff, Louisiana. D. asgum De Gregorio is synonymous. More than equally 

 abundant is the D. mississippiense Conrad of the Jackson and Vicksburg 

 Eocene, which is also found at Martin Station in Florida. The Prairie Creek 

 beds also contain a pretty species, 9 to 10 mm. long, and about a millimeter in 

 greatest diameter, which I have called D. Eugenii, in honor of Prof Eugene A. 

 Smith, State Geologist of Alabama. It is notable for its quadrangular section, 

 with the convex side of the shell a little narrower than the concave side, the 

 four angles pronounced, the surface between them longitudinally sharply 

 striated, the anterior orifice oblique, and the posterior transverse and inter- 

 nally circular and simply truncate. The shell is rather solid for one of such 

 small size, and strongly arcuated. D. afnmlatiim Meyer has a name several 

 times preoccupied, which is of the less importance since his she] 1 is probably 

 a young specimen of minutistriattim in which the longitudinal sculpture has 

 not developed, as often happens. D. bitubattim and D. Danai Meyer, with D. 

 gniziim De Gregorio, are all dubious Eocene forms. D. dc7isatiim Conrad, from 



