18 THE NAUTILUS. 



published in Archiv f iir 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, Uniotiidce and 31utelidce,'^ 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 into a larger group or super-family, 

 which he calls the Najidcv. He finds in all the genera which he 

 places in the Unionidce, the larval state is a glochidhim, 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 Mutelidce, pass 

 through a state after hatching which he calls a lasidium, 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 A])lodo7i, having a few South American species, hitherto placed 

 in Monocondyloea, 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 Monocondylwa 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 Sudamerika, von H. von Jhering. Jahrg 59, 1 Bd., 1 Heft. 



' Fischer, Manuel de Conchyliologie, p. 997, divides Unionidce into two sub- 

 families ; Uiiiouina including Unio, Monoctvidylcea, Pseudodon, Anodonta, 

 Solenaia and Mycetopus ; 2d Muielina, with Miitela, Ilyria, Caslalia and Leila. 



