MOLLUSCA. 679 



elevation about once and a half as great as the diameter of the 

 last volution, and the last volution when measured on the aper- 

 tural side forms about three- fourths oi the entire height; volu- 

 tions convex, not inflated, but regularly rounded, with a well 

 marked suture in the casts, the only condition in which they are 

 known from. New Jersey, but which does not indicate a flattening 

 at the top in the perfect shell ; aperture elongate-ovate, acutely 

 rounded below and somewhat sharper above than below, the 

 greatest breadth being below the middle; base of the last volution 

 sharply rounding into the umbilical cavity; umbilical opening in 

 the cast small, not extending above the lowest volution, and show- 

 ing no evidence of any thickening or callus of any kind ; surface 

 unknown." (Whitfield.) 



Remarks. This species is a common one in the faunas of the 

 Navesink marl, where it usually occurs in the form of internal 

 casts. These casts are certainly identical with similar specimens 

 from Alabama, and with Mississippi specimens which retain the 

 shell. These southern examples, however, have never been identi- 

 fied with the New Jersey species, but have usually been referred to 

 L. rectilabrum Con., or L. obliquata H. &. M. Gabb has dis- 

 cussed the relations of these two species, 1 and considers them to 

 be identical, but he makes no mention of L. halli in that connec- 

 tion. It is not improbable that all these shells belong to a com- 

 mon species, which ranges from New Jersey to the Gulf border, 

 and then into the northwestern interior region, in which case the 

 name L. obliquata would take precedence and all the other names 

 be dropped as synonyms. 



Some examples of the casts of this species apparently have a 

 distinctly flattened band on the upper side of the volutions 

 adjacent to the suture, and it is apparently such specimens as this 

 that Whitfield has incorrectly referred to Gyrodes altispira; 

 among a large number of casts from Mullica Hill, however, all 

 gradations between specimens with such a flattened border and 

 those which are rounded may be selected, and all are apparently 

 members of a single species. 



'Proc. Acad. Nat. Sci. Phil. (1876), p. 296. 



