1558 CRUSTACEA. 



the Cancroids, which belong mainly to warm waters, does not include 

 a single genus exclusively American, and of the family Leucosidae, of 

 the Leucosoids, there are only three known species. 



We also perceive why the western coast of America has no zoolo- 

 gical affinity with the Pacific Islands. The temperature of their 

 waters is widely different; and, moreover, the oceanic currents of the 

 tropics run from the American coast to the westward, and are a 

 barrier to migration eastward. 



The relations of the American or Occidental to the Africo-European 

 kingdom are of much interest. The two kingdoms are widely diffe- 

 rent in most respects. 



In the first place, the genera Lupa, Gelasimus, Ocypoda, Libinia, 

 Epialtus, Hepatus, well represented on the American coasts, are not 

 known on the European, besides others (Table 1, page 1548) of less 

 prominence. 



Again, there are several genera common in Europe, not known in 

 America, as Inachus, Maia, Achceus, Portunus, Ebalia, Latreillia, 

 Aflianas, in addition to those included in Table 2, on page 1548. 



Still, the American and Africo-European kingdoms have a common 

 character separating them from the Oriental. For example : the 

 great genus Cancer occurs in both of these kingdoms, and is not known 

 in Oriental seas, except in New Zealand and Tasmania. So also the 

 important genus Homarus; besides Hyas, Herbstia, Leptopodia, Atelecy- 

 clus, Munida, and Grimothea. The genus Homarus has one species on 

 the coast of the United States, one on the coast of Europe, and one at 

 Table Bay, South Africa, thus ranging over the whole Atlantic. 



We may now treat separately of the several Kingdoms, and their 

 subdivision into Provinces, pointing out the naturalness of their limits, 

 and the characteristics of these Provinces. Each temperature region 

 along a coast makes a distinct Province, which facts, where ascer- 

 tained, show to be well characterized. In some cases, a farther sub- 

 division may be desirable, and when so, the subordinate divisions may 

 be called Districts. The Provinces of each zone together may consti- 

 tute a,'Subkingdom, as the Torrid Subkingdom, Temperate Subking- 

 dom, &c. 



