270 Dr. A. Alcock on a neio 



The state of affairs is exliil)ited in the preceding- table, 

 from which I have eliminated Purdjxigurus, as it is rather 

 abyssal than sublittoral, and Enixigurus^ as it is cosmopolitan 

 and as much littoral as sublittoral. And I must emphasize 

 the fact that the reference is to sublittoral genera only, i. e. 

 to groups the majority of species of which live on the sub- 

 marine " shoot ^^ or continental slope. [The land and littoral 

 hermit-crabs of India are, by the evidence both of genera 

 and species, parcel of a tropical marine province tiiat extends 

 from the coast of East Africa to the eastern confines of 

 Polynesia.] 



§3. The Distribution of the C^cilhd^ explicable on 

 THE Theory of a Tethyan Sea. 



Now the point to which I would here draw attention is 

 that the regions where these sublittoral hermit-crabs are 

 concentrated show some remarkable coincidences with those 

 where HerpeJe and the Ccvciliid^ in general are found; and 

 it seems to me that we have here (quite apart from any other 

 sources of evidence) some conceivable outlines of a sea or 

 chain of archipelagoes that may at some former time have 

 extended, under uniform conditions, north of the Equator, 

 from Panama eastwards, by way of Africa, into South-east 

 Asia. Of this sea the hermit-crabs in question might be 

 supposed to be part of the residual littoral or sublittoral 

 fauna, while Ilerpeh might be one of the relics of the land- 

 fauna of its southern coasts. 



As to the time when this great sea may be supposed to 

 have existed, all that can here be said is that the Cajcilians 

 are quite unknown in a fossil state and that the earliest 

 indisputable remains of Paguridse are referred by palason- 

 tologists to the Eocene. 



It is, perhaps, hardly necessary to remark that the southern 

 limits of this supposed sea correspond fairly well, both in 

 space and time, with Professor Suess's Tethys. 



Nor, perhaps, is it necessary to state that numerous other 

 writers, both geologists and zoographers, have discussed the 

 question of former land-connexions between India and Africa 

 on the one hand and between Africa and South America on 

 the other, and that the connexion between India and South 

 Africa is regarded by many competent geologists as suffi- 

 ciently established by evidence. This connexion, which is 

 well known by the name "Lemuria,^' is believed to have 

 included Madagascar, and may have extended into the 

 Tertiary period ; it explains the presence of Ca3cilians in tiie 

 Seychelles and the absence of the hermit-crabs in question 

 from the cast coast of Africa. 



