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Show 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, Krefft1, from New South Wales, was at least one third larger than 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 33 c. cm., weighs about 2000 grammes. „ p, „ 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 favourably with the proportions in man, in whom, taking the average capacity as 1500 c. cm., and the average weight as 65,01)0 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 proportion to their weight than larger ; and in the other by the increase of the weight of the specimens of Echidna by the 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 m m . in length, I find to be 17 c. cm., and therefore only equal to the very 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 :- 1. The inhabitants of a wet and cold climate need a warm covering. 2. A moist and fertile soil is heavier to work than a dry and sandy one. 3. A cold climate produces greater size, and, at the same time, 4, a reduction and shortening of extremities. [ ? 5. O n moist and heavy soils there is a less supply of carbonate of lime available for bone-making purposes than on sandy.] 1 Ann. Mag. N. H. (4)i. p. 113 (1868). Probably the same as E. ramsayi, Owen, Phil. Trans, clxxv. p. 273, pi. xiv. (1881). Result. Long thick hair of var. setosa. Greater digging power of var. setosa by increase of length of third hind claw. Greater size, especially marked by larger skull and brain-capacity of setosa. Shorter snout of var. setosa. Greater tendency of var. setosa to have open vacuities on base of skull. |