ix CHARACTERS OF ELEPHANTIDAE 217 



with abundant air cavities in the roofing and other bones. The 

 incisors are developed into long tusks, which exist in the upper 

 jaw alone, in the lower jaw alone, or in both jaws. There are 

 no canines. The molars are lophodont. The clavicle is absent. 

 The femur has no third trochanter. The bones of the carpus are 

 serially arranged and do not interlock. The stomach is simple. 

 The brain has much convoluted cerebral hemispheres, but the 

 cerebellum is completely uncovered by them. The intestine is 

 provided with a wide caecum. The testes are abdominal. The 

 teats are pectoral in position. The placenta is non-deciduate and 

 zonary. There are two venae cavae superiores. 



The position of the limbs in the Elephant tribe is unique among 

 living animals : their straightness that is to say, and the absence 

 or very slight development of angulation at the joints of the 

 limb bones. This same feature has been observed in the extinct 

 Dinocerata and in the Titanotheria. It must not, however, be 

 assumed from the resemblance to these ancient forms that there is 

 much affinity between them and the Proboscidea, or that the latter 

 have retained an ancient feature of organisation. The oldest 

 Ungulates for the most part, and the Creodonts to which they are 

 undoubtedly related, have much bent limbs. It must be considered, 

 therefore, that the arrangement obtaining in the Elephants is purely 

 secondary. Professor Osborn has put forward the reasonable view l 

 that the vertical limbs of all these colossal creatures are due to 

 "an adaptation designed to transmit the increasing weight" of 

 these animals. The huge bulk of the body is better borne by 

 vertical pillars than by an angulated limb. Other points, however, 

 such as the exposure of the cerebellum, the two venae cavae, the 

 five digits, and the absence of a third trochanter, argue a low 

 position for the Proboscidea in the Eutherian group. 



The group can be readily divided into two families, the 

 Elephantidae and the Dinotheriidae. We will commence with 

 the former. 



The Elephants proper, Elephantidae, differ from the Dino- 

 theriidae in, and are characterised by, a number of anatomical 

 features. They possess long tusks (incisors) either in both jaws, 

 or, if only in one jaw, in the upper. The molar teeth are very 

 large so large that only a few of them are simultaneously in use. 

 There are but three definable genera of Elephantidae, of which 



1 American Nat. February 1900, p. 89. 



