960 The American Naturalist. [November, 
Zoological News. — Mollusca. — According to MM. Bornet 
and Flahault, the chief cause of the disappearance of shells in quiet 
bays where they are not subject to wave action is the constant gnawing 
away of the calcareous matter by shell-boring algae and fungi. Ten 
genera of boring plants are described, and, in some cases, the life- 
histories are narrated. (Bull. Soc. Bot. France, t. 36.) 
Pisces.—The Bull. U. S. Fish. Com. for 1892 includes a paper by 
Dr. Eigenmann on the viviparous fishes of the Pacific Coast of North 
America. The author reviews the Embiotocidae, gives a bibliography 
of the viviparous fishes, and a detailed accout of the development of 
Cymatogaster from fertilization to hatching, and the details of the de- 
velopment of the intestine and Kupffer’s vesicle. Outlines of the post- 
embryonic development are also presented. 
According to Dr. Gill, the proper generic name of the Tunnies 
is Thynnus. A discussion of the question is followed by a list of the 
synonyms. (Proceeds. Natl. Mus., Vol. XVI, No. 965.) 
The same author has published a provisional arrangement of the 
families and subfamilies of fishes which includes the names of the pro- 
posers and modifiers of family names with the dates of naming. (Sixth 
Mem., Vol. VI, Natl. Acad. Sciences.) 
Mammalia.—Dr. J. A. Allen calls attention to the cranial varia- 
tions due to growth and individual differentiation, and instances the 
species Neotoma micropus as a case in point. In a series of fifty skulls 
of this species it would be easy to select extremes that depart so widely 
from the average in one or more characters that they might readily be 
supposed to represent distinct species. Hence the determination of the 
status of a species described from one or two specimens must depend 
upon the subsequent examination of a large amount of material bear- 
ing upon this and its closely-related forms. (Bull. Am. Mus. Nat. 
Hist., Aug., 1894.) 
