138 Trans. Acad. Sci. of St. Louis. 



the very obtuse base of the shell, absence of canal and in the 

 very small anal sinus situated well behind the peripheral 

 carina ; one of these genera may be named as follows : — 



Toniopleura n. gen. 



In this genus the form is rather slender and elongate, with 

 acute many-whorled spire and a small smooth and generally 

 paucispiral embryo ; the aperture is usually about a third as 

 long as the shell. The whorls have each two larger and 

 more conspicuous smooth spiral carinae, one just below the 

 suture, the other at about the middle and also a few other 

 smaller carinae. A moderately concave fasciolar surface, 

 bearing the small but deep anal sinus, is situated between the 

 two principal carinae. Lines of growth generally coarsely 

 incised and very conspicuous, as in Pleuroliria. The species 

 are moderate or small in size and rather numerous, those be- 

 fore me being labeled P. nivea Phil., the type of the genus, 

 poidoensis Jouss., makimonos Jouss. and violacea Hinds. 

 Such species as cincta Lamk. and bijubata Reeve, resemble 

 typical Tomopleura in general form and sculpture and partic- 

 ularly in the obtuse base, absence of beak and form and pos- 

 terior position of the anal sinus, but the absence of distinct 

 lines of growth, generally acute and substyliform apex and 

 some other characters would seem to indicate that they are at 

 least subgenerically different. 



Among the generic types which may be considered in man} 7 

 respects intermediate between the more typical Pleurotomids 

 which precede and the allies of Surcula to be mentioned below, 

 may be cited Scobinella Con. (= Moniliopsis Cou., and Zelia 

 De Greg.), Eucheilodon Gabb, Glyptotoma n. gen., Sinis- 

 trella Meyer, Trypanotoma Coss., Clinura Bell., Cochlespira 

 Con. ( = Ancistrosyrinx and Candelabrum Dall), Cochlespirop- 

 sis n. gen., Protosurcula n. gen., Eosurcula n. gen., Cochle- 

 spirella Csy., Microdrilla Csy., Aforia Dall, Antiplanes Dall, 

 Bathytoma H. and B., and Megasurcula n. gen. These genera 

 are all devoid of true ribbing, as in the preceding typical 

 Pleurotomids, but have the spirals less developed. The great 



