1805. PROCEEDINGS OF THE NATIONAL MUSEUM. 329 



doiita hcr'nu liana, MicUlendort", collected by J)r. Dall at Petropaulovski, 

 Kaiiichatka. This I have verified by comparing- the types with Dr. 

 Dairs shells. 



Inio ravistissus, Kobelt, of Afg'hauistan, appears to be a member of 

 one of the great European groups. Two Uuios have been credited to 

 Oregon, U. famelicus of Gould, and U. oregonensis of Lea. The types of 

 both of these species are in the jSTational Mnseum collection, and I can 

 say without hesitation that the former is a young shell of U. multi- 

 striatKfi, Lea, of Brazil, while the latter is only an old, rather large 

 and solid T\ roirelli, Lea, of Central America. Unio marfjaritiferiis, 

 Linnauis, is the only species of the genus known at present in the 

 Pacific drainage of i^Torth America. 



Although there is a slight mingling of the forms of this and the 

 Oriental regions in the Amoor Valley and northern Jai)au, I only know 

 of one group, represented by a single species, belonging to the Pahe- 

 arctic i)rovince which is extralimital, this being Unio margaritiferus, 

 Linnaeus, which is found in the Upper Missouri of the Mississippi area, 

 and in eastern Canada and New England of the Atlantic drainage. 

 Of its distribution, more will hereafter be said. On the other hand, 

 I do not know of a single Naiad belonging to any other province, which 

 is found within this great region. 



The Ethiopian Region. — All the continent of Africa lying south of the 

 Desert of Sahara, including the Nile to its mouth, is peopled by a 

 common assemblage of Naiad life. The only genera of the TTnionid<e rep- 

 resented in this region are Unio, which is distributed over the whole 

 territory, and Biirtonia (if it be a valid genus), with a few species con- 

 lined, so far as is known, to the region of the Great Lakes. All the 

 Uuios are small to medium in size, and are not particularly striking in 

 any way. A large proportion of them are more or less covered with 

 slight zigzag or reticulated delicate sculpture, and in this particular, as 

 well as in form and texture, they recall the LTnios of India. This is 

 especially true of the forms known from the Cape region. A few 

 species which 1 have not seen, have been reported on rather doubtful 

 evidence from Madagascar. 



Within this area are found five genera of the Mutelidie: Mutela, 

 ^patha, and Pleiodon, having a wide distribution, and Brazzmi and Cke- 

 lidonopsis, which are probably more restricted. Little is known as yet 

 of the Naiades of this great territory, but long ago it was remarked by 

 Morelet that the fauna, including the land and fresh-water mollusks of 

 this entire region, was remarkably homogeneous. Several of the groups 

 of Unio and of the Mutelidaj appear to be distributed over the greater 

 part of the province. So far as I know, no species or group of the 

 Naiades belonging within it is found outside of the region, nor is there 

 an immigrant from any other area within its borders. Tlie ocean and 

 the Desert of Sahara appear to be absolute barriers to the ingress or 

 egress of Naiad life. 



The Oriental Region. — All that part of Asia lying south of the great 



