Casey — Notes on the Pleurotomidae. 157 



throughout is very nearly as in elegans but with larger and stronger ribs. 

 Length of the embryo and first three spire whorls, 2.7 mm. ; width, 1.5 



mm. Lower Claiborne Eocene of St. Maurice, La acata n. sp. 



Embryo larger and much stouter than in acuta, fully as wide as high, acutely 

 pointed, the nucleal tip being small and rather elevated, the whorls four 

 in number, closely coiled, feebly convex, all highly polished and devoid 

 of sculpture, the lowermost only acquiring a few riblets In its last quad- 

 rant, which riblets merge gradually into the ten or eleven ribs of the 

 body whorls; lyrae and fasciolar surface nearly as in the two preceding 

 species. Length of a specimen consisting of the embryo and one com- 

 plete body whorl, 1.9 mm.; width, 1.0 mm. Lower Claiborne Eocene of 

 St. Maurice, La obsoleta n. sp. 



The species described by Harris under the names vaughani 

 and sylvaerupis also belong to this genus, but, besides differ- 

 ing from those of the table to some extent in the form of the 

 embryo, have the ribs less numerous and relatively larger; 

 the Upper Claiborne haumonti may likewise be included as a 

 slightly aberrant or degenerate member. A considerable num- 

 ber of specimens of elegans were obtained, but none with 

 more than two body whorls, and it is probable that it may 

 really be a small species when mature ; in this case it would 

 contrast greatly with vaughani and sylvaerupis, which are 

 moderately large species with a many-whorled spire. 



Lieptosurcula n. gen. 



In this genus the form is very slender, fusiform, the canal 

 very long, the aperture and canal together being about half as 

 long as the entire shell. The embryo is relatively very large, 

 higher than wide, conical and composed of five or six polished 

 whorls, the lower whorls gradually acquiring close-set longi- 

 tudinal riblets, and then, equally gradually, the spiral lyrae. 

 The type is the very isolated P. headata * Harris, of the Texas 



* The name <' beadata " is of an etymology difllcult to ascertain. If it 

 is derived from the English word bead, referring to the beaded subsutural 

 collar, it is indeed a " barbarism," or, at any rate, a procedure in the forma- 

 tion of specific names which is generally condemned. It is, however, per- 

 haps not so much worse than mortoniopsis &n(l tezanopsis — Latin and 

 Greek hybrids which have been used by two of our authors, — or such 

 words as texacona, texagyra, texacola and texalta, which have been employed 

 by Prof. Harris. 



