224 Wisconsin Academy of Sciences^ Arts and Letters. 



The absence of Lyssoraanii in Europe and northern Africa would seem 

 to indicate that the ancestors of this group of spiders during the miocene 

 tertiary ranged through northern Asia and YA\a.t is now British America. 

 The connection existing between Alaska and northeastern Asia, as shown 

 by the flora of that epoch, would j)resent no obstacle to a group of spiders 

 originating on one of the continents passing over into the other. The 

 advent of the Glacial Epoch, we may suppose, drove the Lyssomanii, which 

 even then had separated into two genera corresponding to our Asamo- 

 nea and Lyssomanes, members of both of which occurred on either conti- 

 nent, southward, on the one hand through Asia and on the other hand 

 through North America.. The distance which the species are driven is 

 considerable, as none seem to have remained on what is now the Asiatic 

 Continent, but all passed over to Ceylon and the neighboring Madagascar, 

 whence some probably wandered to South Africa. Similarly in North 

 America the species were forced southward to Central America, whence 

 some migrated to South America. Here the conditions were most favor- 

 able to the development of species as the majority of existing forms is 

 reported from this continent. It is still doubtful whether or not the single 

 species in the island of San Domingo and the single species in the southern 

 United States are to be regarded as forms which were left behind in the 

 wholesale migration of the group or whether they are species which have 

 migrated northward from South America since the close of the Glacial 

 Epoch. We incline to the latter supposition, since it is more probable that 

 a limited number of species would undertake a northward migration than 

 that such a limited number would be spared under conditions which were 

 fatal to the existence erf a whole group in the eastern hemisphere. It is, 

 of course, also possible that the Central American species have migrated 

 northward since the close of the Glacial Eijoch. 



It is interesting to note a somewhat similar distribution in another family 

 of sjDiders, the Archaeidse. This family includes four genera; one of these 

 is extinct, and is represented by fossils in the Baltic amber of the Tertiary 

 period; of the three genera that are represented by living species; one is 

 found in Madagascar, one in western Africa, and one in the southern part 

 of South America.* 



FAMILY ATTJD^45. 



SUB-FAMILY LYSSOMAN.^. 



Eyes in four transverse rows. 



Group I. Lyssomanii. Cephalothorax low or moderately high, rather 



elongated, longer than wide. 

 Group II. Athamii. Cephalothorax high, short, quadrate. 

 Group III. Simonelhi. Cephalothorax nodose; spiders ant-Uke in form. 



* E. Simon, Ann. Mus. Civ. di Storia Naturale di Geneva, V. XX, 1884. 



