1885.] MR. O.THOMAS ON THE RACES OF ECHIDNA. 337 



very long time in Australia — long enough in fact to eliminate any 

 specially tropic-loving tendencies it may have inherited from the 

 ancestors common to it and to Proechidna. 



In this connection it should be just noted that the Pleistocene 

 species E. oweni, Krefft\ from New South Wales, was at least one 

 third larger tlian the largest existing species of the family. 



Comparing the skull-capacity of these Echidnas with the total 

 weight of their bodies, we find that (after being in spirit some 

 years), 



Specimen w, with a capacity of .S3 c. cm., weighs about 2000 grammes. 

 » Ih „ 30 „ 2600 „ 



» q, „ 27 „ 2800 „ 



The capacity in cubic centimetres going into the weight in grammes 

 respectively 60, 87, and 104 times ; and thus comparing very favour- 

 ably with the proportions in man, in whom, taking the average capacity 

 as 1500 c. cm., and the average weight as 65,0(10 gr., the former goes 

 into the latter 43 times. This rough comparison is. however, affected 

 in one direction by the general rule that smaller animals have higher 

 capacities in [)roportion to their weight than larger ; and in the other 

 by the increase of the weight of the specimens of Echidna by tlie 

 spirit which had soaked into the flesh, and could not be dried out. 

 The thick coat of spines also must add an appreciable amount to the 

 weight of so small an animal. 



The cranial capacity of a fine Ornithorhynchus, with a skull 

 113 mm. in length, I find to be 17 c. cm., and therefore only equal 

 to the yery smallest of the Echidnas examined. 



To sum up the general conclusions arrived at, we find that certain 

 well-known laws of climatic and geographical variation have caused 

 the original Echidna to show certain modifications at the extremities 

 of its range as follows : — 



Result. 



1. The inhabitants of a wet and Long thick hair of var. setosa. 



cold climate need a warm 

 covering. 



2. A moist and fertile soil is Greater digging power of var. 



heavier to work than a dry setosa by increase of length of 



and sandy one. third hind claw. 



3. A cold climate produces Greater size, especially marked 



greater size, and, at the same by larger skull and brain- 



time, capacity of setosa. 



4. a reduction and shortening Shorter snout of var. setosa. 



of extremities. 

 [ ? 5. On moist and heavy soils Greater tendency of var. setosa 

 there is a less supply of to have open vacuities on base 



carbonate of lime available of skull, 



for boue-rnaking purposes 

 than on sandy.] 



• Aun. Mag. N. H. (-1) i. p. 113 (1868). Probably the same as E. ramayi, 

 Oweu, Phil. Tivans. clxxv. p. 273, pi. siv. (1881). 



