AMERICAN ZOOLOGISTS AND EVOLUTION. 113 



tooth in the mammals of the present day. He finds that the type of 

 the superior molar tooth of the mammals of the Puerco epoch was tri- 

 angular or tritubercular — that is, with two external and one internal 

 tubercle. Of forty-one species of mammals of this epoch all but four 

 of them had this type of tooth. He finds that this tooth exists to-day 

 only in the insectivorous and carnivorous marsupials. In brief, he 

 shows a gradual change taking place from the early primitive type of 

 tooth in the gradual development of another tubercle. The same au- 

 thor,* in defining the characters of an ancient order of mammals, the 

 Amblypoda, says they are the most generalized oi-der of hoofed mam- 

 mals, being intermediate in the structure of their limbs and feet be- 

 tween the Proboscidia, the Perissodactyla, and Artiodactyla, which 

 fact, together with the small size of the brain, places them in anteced- 

 ent relation to the latter, in a systematic sense, connecting them with 

 the lower mammals with small and smooth brains still in existence ; 

 and in a phylogenetic sense, since they precede the other orders in time, 

 they stand in the relation of ancestors. 



Professor Cope,f in a paper read before this Association on the 

 " Classification of the Ungulata," gives special attention to the arrange- 

 ment and character of the carpal and tarsal bones. He shows that 

 " the weaker structure of the carpus and tarsus appears first in time ; 

 that the stronger structure appeared first in the posterior limbs, and 

 that the interlocking structure has greatly multiplied, while the linear 

 has dwindled and mostly disappeared. Here is a direct connection 

 between mechanical excellence and survival." 



In the light of Mr. Caldwell's unquestionable determination of the 

 oviparous character of that curious mammal, the duck-bill mole, asso- 

 ciated with its known reptilian bearings as deduced from its skeleton 

 and other features, the deductions of Professor Cope \ regarding the 

 " Relations between the Theromorphus Reptiles and the Monotreme 

 Mammalia " are of great interest. 



In the Theromorpha are two divisions, one of which, the Pelyco- 

 sauria, is limited to the Permian, and of one of this group he makes 

 the following comparisons : " 1. The relations and number of the bones 

 of the posterior foot are those of the Mammalia much more than those 

 of the Reptilia. 2. The relations of the astragalus and calcaneum to 

 each other are as in the Monotreme Platypus anatimis. 3. The articu- 

 lation of the fibula with both calcaneum and astragalus is as in the 

 Monotreme order of mammals." In brief, he shows the affinity of this 

 reptile to be with the monotremes, and that the affinities are very im- 

 portant in the light of Mr. Caldwell's researches, and the further fact 

 that the development of the egg is meroblastic confirms, so to speak, 

 the reptilian affinities of the monotremes. 



* Wheeler's "United States Geographical Survey," vol. iv, part ii, p. 182. 



t " Proceedings of the American Associated Antiquarian Society," vol. xxxi, p. 47^. 



1;. Ibid., vol. xxsiii, p. 471. 



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