PLEUROTOMIDZ. 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 Pleurotomide 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., 71 species. 
Weinkauff, in Ktster’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 Jahrbucher 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, . : : adel soit Of) 
Weinkanff, Jahrb. Deutsch. Mal. Gesell., iii, 1, . 1876 
_ Tryon, Structural and Systematic Goneneiney a 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 Pleurotomidz 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. 
A Famity PLE UROTOMIDZ. 
Subfamily Pleurotomine. Operculum oval, with terminal 
nucleus. 
Subfamily Clavatuline. Operculum pyriform, with lateral, 
internal nucleus. 
Subfamily Mangiliine. No operculum. 
