14 THE NAUTILUS, 



columella simple, without plaits ; margin of the aperture continuous, 

 simple, thickened, the callus on the body whorl elevated parallel with 

 the outer lip ; aperture narrow, almost linear, slightly effuse at the 

 extremities, as long as the shell. 



" Type O. meekii, Dall. Plate 33, figs 3 and 4." 

 I dedicated this interesting shell to my friend, Hon. T. H. Al- 

 drich, of Birmingham, Alabama, who solved the problem of its gen- 

 eric position, and whose contributions to our knowledge of Tertiary 

 Paleontology are so well known and highly valued. It will be fig- 

 ured on a future plate of this volume. 



NOTE ON THE GENUS PTERIDES. 



BY H. A. P1LSBRY. 



In my study of this group of Mexican freshwater shells I over- 

 looked an important article by the late Professor Sp. Brusina in the 

 Nachrichtsblatt derDeutschen Malak. Gesellschaft for 1906, p. 154, 

 in which he erects the new genus Lanzaia for the long-forgotten 

 Turbo elephantotus of Megerle von Miihlfeldt, described in 1824 from 

 the coast of Dalmatia, and rediscovered by Prof. Brusina, on the 

 seashore near the mouth of the little river Zernovica. 



This snail, Lanzaia elephantota as it will now be called, which is 

 well figured in the Nachrichtsblatt (p. 158), has the aperture formed 

 like that of my Pterides pterostoma (Nautilus xxiii, pi. 5, figs. 1, 2). 

 It differs from the Mexican Pterides by having sinuous flat-topped 

 riblets with close, fine spiral strise in the intervals, and a rather large 

 umbilicus. The Mexican Pterides has a smooth surface, merely 

 rimate umbilicus, and more elongate shape. 



The finding in Mexico of Mediterranean region genera, such as 

 this one, Emmericia and Coilostele is extremely interesting and im- 

 portant. The more prominent groups of freshwater shells are widely 

 diverse. 



