Casey — Notes on the Pleurotomidae. 151 



Orthosurcula n. gen. 



Before proceeding to define some of the more typical allies 

 of Surcula, it will be of advantage to refer to a generic type as 

 named above, combining some of the features of the preced- 

 ing group and the true Surculids. The species are large, 

 moderately stout, completely devoid of ribbing and have the 

 beak elongate, tapering, relatively slender and straight. The 

 spirals are close-set, moderate or small in size, sometimes 

 granulose, and the whorls are more or less broadly inflated 

 below and feebly concave posteriorly. The outer lip projects 

 in the middle as a broad rounded lobe beyond the juxta- 

 sutural part, with the sinus large and posterior, as in Surcula, 

 and the embryo is paucispiral. The types are the upper Eocene 

 PI. longiforma Aid., of Red Bluff, Miss., and the European 

 Eocene Surcula transversaria Lamk. These species have 

 much finer sculpture than the living Surcula auslralis Lamk., 

 which is also an Orthosurcula. 



Surcula H. et A. Adams. 



Turricula Schum. (nom. praeocc). 



This genus is composed of a moderate number of more or 

 less large species, stout in form, with the beak somewhat elon- 

 gate and the columella distinctly twisted, the beak generally 

 having a distinct oblique external ridge which is wholly want- 

 ing in Orthosurcula. The surface has numerous short oblique 

 costae, confined throughout to the peripheral ridge, and, in a 

 few species such as tomata only visible on thenepionic whorls, 

 becoming lost on the larger whorls — like the peripheral dentic- 

 ulation of some forms of Gemmula. The embryo is small 

 and paucispiral. The median parts of the outer lip project 

 beyond the juxta-sutural part in a broad rounded lobe and 

 the sinus is large, rounded and posterior, in these respects 

 resembling Bathytoma and Megasurcula. The type is S. 

 javana Linn. (=nodifera Lamk.), from the coast of China, 

 and the genus will include as well tuberculala Gray, tomata 



