MOLLUSCA. 765 



1892. Odontofusus rostellaroides Whitf., Pal. N. J., vol. 2 



(Monog. U. S. G. S., vol 18), p. 68, pi. 6, figs. 6-7. 

 1892. V olutomorpka (Piestochilus} mucronata Whitf., Pal. N. 



N. J., vol. 2 (Monog. U. S. G. S., vol. 18), p. 75, pi. 6, 



figs. 12-14. 

 1905. Volutomorpha mucronata Johns., Proc. Acad. Nat. Sci. 



Phil. (1905), p. 25. 



Description. "Shell, as exhibited in the casts, slender, with an 

 elevated and slender spire and prolonged rostral beak, giving an 

 elongate, fusiform outline; volutions five or more, moderately 

 convex and with strongly marked suture lines ; body volution, as 

 seen from the front, forming considerably more than half of the 

 length of the entire shell, and the aperture two-thirds as long as 

 the body volution; elliptical in outline, angular above and pro- 

 longed below ; columella slender, marked by two very oblique 

 folds, which are situated somewhat below the middle of its length, 

 the lower being much the stronger of the two; surface features 

 unknown. There is the slightest evidence on two individuals of 

 distant longitudinal folds on the second volution, but not suffi- 

 ciently distinct to give grounds for a positive assertion that such 

 characters existed." (Whitfield.) 



Remarks. This species was originally described by Gabb as 

 a member of the genus Voluta and was later referred to the genus 

 Volutonwrpha by the same author, under which name, with the 

 subgeneric designation Piestochilus, it was described by Whit- 

 field. Whitfield also described in the same report a new species 

 Odontofusus rostellaroides. A careful study of the types of both 

 these species, as well as numerous other specimens, has led to the 

 conclusion that they are all members of a single specific group. 

 The two genera, Odontofusus and Piestochilus are much alike in 

 their general characters when seen only in the condition of in- 

 ternal casts. Both are more or less fusiform shells with usually 

 a single rather strong columellar fold, though sometimes one or 

 two other and usually fainter folds are developed. The primary 

 difference between the two genera seems to be in the presence or 

 absence of vertical folds upon the shell. With the shells them- 



