PLEUROTOMHLE. 153 



usually apparent in the classification ; so that in studying a 

 group of Pleurotoma it is as absolutely necessary to know how 

 each author who has described species as of that group, compre- 

 hended its characters, as it is to refer to the diagnosis itself. 



The systematic works on the Pleurotomidse are few and very 

 incomplete. They include the following monographies : 



Kiener, Iconographie des coquilles vivantes, 27 plates, illus- 

 trating 57 species. 



Reeve, Monograph of Pleurotoma. Conchologia Iconica, 369 

 species. 



Reeve, Monog. of Mangilia. Conch. Icon., 11 species. 



Weinkauff, in Kiister's Conchylien Cabinet, 172 species. This 

 work is in course of publication, but no portion of it has ap- 

 peared for a considerable period. 



Dr. Weinkauff has also catalogued the species of some of the 

 groups in Jahrbiicher der Deutschen Malak. Gesell., iv, 1877. 



The principal classifications of the family are those of 

 H. and A. Adams, Genera of Recent Mollusca, i, 88, . 1853 

 Bellardi, Moll. Tert. du Piemonte, pt. 2, . . . . 1877 

 Weinkauff, Jahrb. Deutsch. Mai. Gesell., iii, 1, . . 1876 

 Tryon, Structural and Systematic Conchology, ii, 183, . 1883 

 Fischer, Manuel de Conchyliologie, 589, . . . . 1884 



Differing in detail, the three latter are essentially founded upon 

 that of Messrs. Adams. 



Living species of Pleurotomidae are found in all seas ; never- 

 theless certain groups are restricted in distribution. Pleurotoma 

 being tropical and subtropical, Bela boreal, etc. The family is 

 geologically modern, but was very numerously represented in 

 tertiary beds, particularly those of northern Italy. 



FAMILY PLEUROTOMIDJE. 



Subfamily Pleurotominae. Operculum oval, with terminal 

 nucleus. 



Subfamily Clavatulinae. Operculum pyriform, with lateral, 

 internal nucleus. 



Subfamily Mangiliinse. No Operculum. 



