1894. SCORPIONS. 363 



supposed, on the hypothesis of a southern land-connection between 

 the two countries. But this is not the only theory that will account 

 for the circumstance ; for it is possible that the family to which the 

 genera belong had once a wide extension in the Northern Hemisphere, 

 and that although extermhiated, for the most part, in the keener 

 competition of more northern areas, some of the genera, like the 

 Marsupial Mammals, have found places of refuge in the countries 

 to which they are now restricted ; and this supposition is borne out 

 by the fact that a solitary representative of the family has been 

 recently discovered in Sumatra. 



It is necessary to bear in mind that the general absence of 

 similarity between the Scorpions of the three southern extensions of 

 land is not of the same value in disproving the former existence of 

 Antarctica as is the absence of similarity between Madagascar and 

 the Oriental Region in disproving the existence of Lemuria ; for 

 while it is clear that the Scorpions could have freely migrated across 

 a land lying in the centre of the tropical Indian Ocean, it is equally 

 clear that, unless there was a long-continued genial climate in the 

 Antarctic Seas, they could never have succeeded in making their 

 way even along the northern coast-line of the southern continent that 

 Mr. Forbes has delineated. 



A further modification of Sclater and Wallace's Zoo-geographical 

 Map that has been suggested, and often adopted, is the union of the 

 so-called Nearctic and Palaearctic into one region, for which the term 

 Holarctic has been proposed ; but a study of the distribution of Scor- 

 pions affords no support to this change, inasmuch as it shows that 

 none of the genera extend from one region to the other, and even 

 when the families are taken into consideration, it is found that the 

 similarity between the Palaearctic and Nearctic is no greater than that 

 between the Palaearctic and Oriental. 



There still remain one or two apparent anomalies in the distribu- 

 tion of some of the families of Scorpions to be accounted for. The 

 first and strangest of these, furnished by the Ischnuridas, is the 

 unquestionably close relationship that exists between the exclusively 

 South African genus Opisthocentrus and the genus Opisthacantlms, which 

 is restricted to Panama, Colombia, etc. A somewhat similar peculiarity 

 is found in the case of the two known genera of the Diplocentridae, 

 namely, Diplocentrns, which is found in the Antilles and Central 

 America, and Neho, which occurs in Arabia, Egypt, and Syria. Again, 

 coming further to the north, we find that in the luridae the Levan- 

 tine genus lunis has one of its nearest allies in the Californian 

 Uroctonus, and that the Neotropical group of the Chactidae has a 

 South European representative in Euscorpius. 



These four cases, taken together, seem to me to point to the con- 

 clusion that, at one period, these families had a widely-extended range 

 in the Northern Hemisphere, and were enabled thereby to pass from 

 Eastern Asia into Western North America. And the one item of 



