18 THE NAUTILUS. 
published in Archiv fiir Naturgeschichte,' a lengthy article on the 
Najidae of San Paulo, Brazil, and a proposed system of classifica- 
tion in which some startling discoveries are brought to light, and 
which ranks as one of the ablest papers ever written on the subject. 
This classification, while working a complete revolution in our pre- 
conceived ideas of the relationships of the different members of this 
group, is so clear and philosophical, it so thoroughly takes cogni- 
zance of all the known facts, that it is certainly worthy of the most 
thoughtful consideration. In a brief review like this I can only 
allude to the more prominent points, and those who are interested 
should read the paper itself. 
H. and A. Adams, in the Genera of Recent Mollusca, divide the 
Naiades into two families, Unionide and Mutelide,’ separated by cer- 
tain minor characters of the shells and animals. Ihering uses the 
same family names in a somewhat different sense from the Messrs 
Adams, and unites the whole intoa larger group or super-family, 
which he calls the Najide. He finds in all the genera which he 
places in the Unionida, the larval state is a glochidium, that is, a 
stage or condition in which the animal is completely enclosed in a 
porous bivalve shell. 
On the other hand, the species which he places in Mutelide, pass 
through a state after hatching which he calls a dasidium, in which 
the animal is divided into three parts, of which only the middle 
bears the small, single shell. He finds, on examination, that those 
South American forms that have hitherto been placed with Anodon, 
pass through the lasidium stage, hence they must be separated 
from that genus whose larval state is a glochidium, and he retains 
for this group the name suggested by Gray—Glabaris. He believes 
that Aplodon, having a few South American species, hitherto placed 
in Monocondylea, and the so-called African Anodons belong to the 
same family, and that the latter should be placed in Glabaris. 
D’Orbigny established the genus Monocondylea for certain species 
of South American Naiadae whose shells possess a single cardinal, 
and no lateral teeth. Several of these will fall into other natural 
groups. Ihering does not mention the Asiatic species which Lea 
‘Najaden von S. Paulo und die geographische Verbreitung der Siisswasser 
Faunen von Siidamerika, von H. von Jhering. Jahrg 59, 1 Bd., 1 Heft. 
* Fischer, Manuel de Conchyliologie, p. 997, divides Uxitonide into two sub- 
families; Unionine including Unio, AMonocondylea, FPseudodon, Anodonta, 
Solenaia and Mycetopus ; 24 Muteline, with Mutela, Hyria, Castalia and Leila. 
