378 ORTMANX — DISTKIBUTIOX OF DECAPODS [Aprils, 



nent, where presumably their original home was located, is not yet 

 established. It must necessarily have gone over Central Asia. Cray- 

 fishes of the European type are found eastward as far as Turkestan. 

 It is doubtful whether crayfishes are absolutely lacking in the region 

 between Turkestan and the Amur river. None are reported, but 

 these parts are very poorly known. For the present I cannot imag- 

 ine any reason for their disappearance in this region, in which they 

 must have once existed, and therefore it is well to suspend judgment 

 until these parts have been properly investigated.^ 



SUMMARY OF RESULTS OF PART II. 

 A. History of the Continents. 



a. Lower Cretaceous. (See Fig. 5, p. 379.) 



I. During the Lower Cretaceous there existed a Sino- Australian 

 continent, comprising eastern Asia, the Indo- Malaysian Archipelago 

 and Australia, and which was continued to Antarctica. We may 

 retain for this continent the name Sino-Australian, although it 

 is larger than that drawn by Neumayr for the Jurassic time. We 

 are justified in doing this, since probably the Jurassic Sino-Austra- 

 lia also included Antarctica. 



II. Besides, we have 2. Nearctic coniifient : this consists of the 

 larger part of present North Ai7terica, and extended probably across 

 Greenland to the Scandinavian mass of North Europe. This con- 

 tinent also corresponds closely to Neumayr's Nearctica of Jurassic 

 times, and consequently we have retained this name for it. 



III. A third continent was formed by Central America, and we 

 shall call this by the name Antillia. Its remnants are now found 

 in Central America, the West Indian Islands and northern South 

 America (excluding Guiana). This continent is not given by 

 Neumayr for the Jurassic, but probably existed then. 



IV. A fourth continent was formed by the western portion of old 



' A theory lately propounded by C. Y. Wright (see Science^ Vol. 16, Aug. 15, 

 1902, p. 262 f.) would go far toward an explanation of the causes leading to the 

 destruction of the Central Asiatic crayfishes if properly supported. Wright be- 

 lieves that Northern and Central Asia was largely coverad by water in recent 

 geological time, but the evidence introduced lor this is, in my opinion, entirely 

 inappropriate. Of the five points mentioned by Wright two (Nos. 3 and 4) 

 have no bearing at all upon this theory, and the value of the other three, espe- 

 cially of the fifth, is highly questionable. 



