Casey — Notes on the Pleurotomidae. 163 



body whorls measures 27 mm. in length and 12.5 mm. in 

 width. The embryo is of the same general type as in Pseit- 

 dotoma, as figured by Cossmann. 



Fusitoma n. gen. 



The type of this genus is Fusitoma sipho, a rather elon- 

 ofate, fusiform and moderately stout shell with somewhat 

 thin walls, originally assigned to the genus Fusus. The 

 aperture is feebly oblique and half as long as the shell, the 

 canal very short and not diiferentiated from the aperture, 

 of which it forms the gradually narrowed anterior end. The 

 base is very gradually and sinuately narrowed below the 

 broad convexity of the body whorl. The body whorls are 

 broadly convex, becoming concave above near the suture, the 

 latter feebly margined beneath. The ribs are obsolete, being 

 replaced by long fine elevated lines apparently produced by 

 arrested growth and crossed by somewhat conspicuous lyra- 

 tion. The embryo in my single example — which I owe to 

 the kindness of Mr. Aldrich — is not in good condition, so that 

 I cannot venture to describe it. 



There have been some other species described and figured 

 from the American Eocene, which may form genera in this 

 tribe or enter some of those already defined and particularly 

 Fusitoma; among these may be mentioned PI. leania and 

 Pleiirotomella sigma, of Harris, Pleurotoma capax Whitf., 

 Fusus whitfiddi Aid., and perhaps Fusus harrisi, of the 

 latter author. I have not been able to study any of these 

 species except by published drawings and descriptions. 



DONOVANIINI. 



The genus Donovania Bucq. {= Lachesis Risso; noni. 

 praeocc.) is one of those doubtful forms which have been as- 

 signed widely different positions in the Gastropod series, and 

 is included here as forming a distinct tribe of Pleurotomidae 

 merely for the sake of completeness, and not because I have 

 been able to make any investigations leading to personal con- 



