152 Trans. Acad. Sci. of St. Louis. 



Dillw. (=javana Kieuer non Lina.) and fuhninata Kiener, 

 from the ludo-Pacific fauna, and the South Aiv\c?i\\Clavatula 

 gravis of Hinds. Surcida, as far as known to me, is a mod- 

 ern development and most of the very numerous old Tertiary 

 forms will constitute other genera. 



Pleurofusia De Greg. 



This name was given by De Gregorio to a species which he 

 described and figured under the name longirostropsis ^ stating 

 that it may be a variety of servata Con., and indicating the lat- 

 ter species as one of the generic types. Nothing very similar is 

 known to me from the Upper Claiborne ferruginous sand, but 

 there is a specimen in the cabinet of Mr. Aldrich, from the 

 Lower Claiborne, which greatly resembles the figure referred 

 to. At any rate, it seems evident that Pleurofusia, as repre- 

 sented by servata and the specimen alluded to, must be rec- 

 ognized as valid. The species are moderate to rather small 

 in size and of somewhat slender form, with rather slender, 

 somewhat elongate beak and strong, longitudinally and trans- 

 versely rounded, almost entire costae, generally some seven or 

 eight in number. The embryo is conoidal and multispiral to 

 obtuse and paucispiral in form, but never has any conspicuous 

 lonsitudinal riblets. The fasciolar surface is usually well de- 

 fined, in great part obliterating the ribs below the suture, but 

 in some cases is less evident, the ribs being strong thoughout 

 the length of the whorl. The species chiefly characterize the 

 upper Eocene and Vicksburg Oligocene of the Southern States, 

 but would seem to have originated in such forms as langdoni 

 Aid., of the lower Eocene, which has more numerous ribs, 

 and extend upward at least to the lower Miocene of West 

 Florida, where the genus is represented by a species resem- 

 bling servata. The other species known to me are declivis 

 Con. and oblivia, vicksburgensis, evanescens, collar-is and hil- 

 gardi Csy., with several others still undescribed. Such species 

 as servatoidea Aid., will form an allied genus somewhat resem- 

 bling Pleurofusia in the ribbing but differing in the position 

 of the anal sinus and character of the sculpture. 



