Casey — Notes on the Plexirotomidae. 169 



being the very broad shallow anal sinus situated on the peri- 

 phery and not on or near the suture, which is its invariable 

 position in the Daphnellini. The only genus at present 

 known is Taranis Jeffr., a very minute and fragile shell, with 

 the aperture broadly oval and the canal very short. The 

 surface is clathrated by equal longitudinal and spiral raised 

 lines and is without trace of true ribs. The body whorls are 

 about three in number. No extinct species of Taranis is 

 known from the European strata, but, singularly enough, a 

 species which, from the figure, appears to be a true Taranis, 

 was described by Prof. Harris fromjthe middle Eocene strata 

 of Smithville, Texas, under the mime jlnexa (Proc. Ac. Nat. 

 Sci., Phila., 1895, p. 64). This is one of the most interest- 

 ing discoveries yet announced among our extinct Gastropods. 



MlTROMORPHINI . 



The species of this tribe are very small, oval or fusiform in 

 outline and generally strongly, spirally sculptured. The aper- 

 ture is long and more or less narrowly oval, and, owing to the 

 fact that the anal sinus is obsolete, some doubt exists as to 

 their true relationship. In placing the tribe provisionally with 

 the Pleurotomidae I merely follow the usual custom, having 

 made no determinative studies myself. The species seem to 

 be few in number and individually rare or, at least, but few 

 exist in any collection accessible to me at present. The only 

 representative in my cabinet has the apex of the shell worn 

 away so that I am unable to describe the embryo, except in 

 general terms as shown in the West Indian fossil forms de- 

 scribed by Dr. Dall, in which it appears to be small, rounded 

 or obtuse and paucispiral. 



Species of Mitromorpha have been described from Japan, 

 California, the Pliocene strata of Florida and the European 

 Pliocene, the latter, the subulata of Cossmann, apparently 

 being a typical member of the genus; so its distribution, 

 though limited to the northern temperate regions as far as 

 known, is, or has been, very extended. The columella is 

 sometimes bi- or triplicate at the middle, and the outer lip is, 



