NO. 1205. SYXOPSIS OF THE NAIADES— SIMPSOX. 505 



number of forms are fouud in each of them that are not at all closely 

 related to any of those of the other. 

 These regions may be tabulated as follows : 



ARKAS OF THE NAIAP REGIONS.' 



Palearctic 



Mississipiiian . . 



Europe. 



Xorthern and Western Asia. 



North Africa to the iJesert. 



iPacific drainage of North America. 



Ethiopian Africa, south of the Sahara. 



Orients] )Asia, south of the HimaLayas. 



lEast Indies to the Solomon Islands. 



("Australia. 

 Australian -.Tasmania. 



l-New Zealand. Part of New Guinea. 

 Neotroiiical South America. 



f Central America. 

 Central Aniericau- Mexico, east of the Cordillera. 



Icuba. 



Entire Mississippi Valley and the Gulf drainage from west Florida 



to the Eio Grande. 

 Mackenzie Eiver system. 

 Red River of the North. 



.Great Lakes. , 



Atlantic J Lower St. Lawrence and rivers of eastern Canada. 



1 Atlantic drainage of the United States. 



I have hesitated long before placing a considerable number of the 

 species of Southeastern Asia in and near ISTorth American genera. I had 

 hoped to be able to examine the soft parts of a number of these Oriental 

 forms, but have been disappointed, and as nothiug is known of the 

 anatomy of most of them 1 have been compelled to classify by shell 

 characters alone. It is certain that the beak sculpture of a large num- 

 ber of Naiades of this area is essentially concentric, and not zigzag 

 radial, as it is in most of the forms of the Oriental region. The shell 

 characters of the ponderous Chinese Uniones are certainly much like 

 those of Quadrnla in the form, the teeth, the beak sculpture, and 

 especially the deep, compressed beak cavities. A great number of fossil 

 forms from the Tertiary strata of Asia and Eastern Euroj)e seem to 

 show the closest relationship to the American Quadrulas. Hyriopsis, 

 Cristaria, Ghamherlainia, and Pilshryoconcha seem to be related by 

 shell characters to the alate forms of LampsUis, and even the strange 

 Pseudospatha of Africa would appear to belong here. 



I recognize about one thousand species and 82 varieties of Unionidne, 

 having reduced to the synonymy a great many names that most authors 

 have believed to stand for valid species. Of these, 533 species and 55 

 varieties belong in i^orth America and 101 in South America. The 

 list contains 117 species of Mutelidfe and 11 varieties, and of these 80 



' For map of Naiad Kegions see jilate. 



