346 ORTMANN — DISTRIBUTION OF DECAPODS [April*, 



dad and a third in Venezuela is entirely opposed to the drift 

 theory, since under the latter we ought to expect only one species 

 in this whole region. 



Simpson's theory of the origin of the West Indian faunas is sup- 

 ported exclusively by zoogeographical evidence, and, as we have 

 seen, it agrees admirably with the facts presented by the Decapod 

 Crustaceans. But the various changes undergone by the West 

 Indian islands have been investigated also from a geological 

 and physiographical standpoint. I shall disregard the views of 

 Spencer 1 on the Antillean continent, which are certainly exag- 

 gerated, since he makes this whole region land during the Pliocene, 

 even including the floor of the Mexican Gulf and the Caribbean 

 Sea. According to him, the Pliocene land would have been ele- 

 vated above the present level to the amount of one and one-half to 

 two and one half miles, and this would result in a wide connection 

 of both North and South America with the Antillean land. But 

 this is simply impossible. If such a land connection had existed 

 in Pliocene times, it should have left not only unmistakable traces 

 in the present fauna of the Antilles, but the Antillean fauna ought 

 to be practically identical with that of the southern parts of North 

 America and the northern parts of South America; but this is by 

 no means the case. Nevertheless, one of the items in Spencer's 

 theories is important for our purposes. This is the assumption of a 

 Pliocene elevation of these parts, succeeded by the opposite move- 

 ment at the end of the Pliocene and in the Pleistocene. 



On the other hand, Hill 2 assumes for Cuba a subsidence at the 

 beginning of the Tertiary. This is followed, in the older Pleisto- 

 cene, by a rapid elevation, continuing more or less continuously up 

 to the present time. This late Tertiary and recent elevation influ- 

 enced also the neighboring parts of the Gulf of Mexico and the 

 Caribbean Sea, and Hill concedes that it was possible that Cuba 

 extended then as far as Yucatan, thus connecting with. Central 

 America. 



The views of Hill and Simpson agree only in part as to the gen- 

 eral movements of these regions. Simpson assumes an Eocene 

 elevation and land connection, while Hill's elevation is Pleisto- 

 cene. But it is quite possible that both are correct. We have 



1 Spencer, J. W. : " Reconstruction of the Antillean Continent " (Bull, Gee- 

 log. Soc. America, Vol. 6, 1895). 



* Bull. Mus. Harvard, Vol. 16, 1895. 



