THE PLACENT/E OF THE EDENTATA. J 1 I 



or cotyledons, in connection with which no decidua is developed, 

 or is it a true deciduate placenta, resembling that of the Car- 

 nivora in the essentials of its internal structure as in its external 

 form ? Recent investigation lias convinced me, that, in both 

 these animals, the placenta is as truly deciduate as that of a 

 Rodent ; so that most unquestionably, if the placental method of 

 classification is to be adopted, both Elephas and Hyrax must go 

 into the same primary division of the Monodelphia as the 

 Rodentia and Carnivora, 



But do these facts really present obstacles to the placental 

 system of classification ? 



So far as the case of the Elephants is concerned, I must con- 

 fess that I see no difficulty in the way of an arrangement which 

 unites the Proboscidea more closely with the Rodentia than with 

 the Artiodactyla and Perissodactyla, the singular ties which unite 

 the Elephants with the Rodents having been a matter of common 

 remark since the clavs of Cuvier. 



In the absence of any definite knowledge of the placental 

 structure of Rhinoceros and Tapir us* it would, perhaps, be pre- 

 mature to discuss the position of Hyrax, as determined by its 

 placenta ; but if it should eventually appear, as is very probable, 

 that Rhinoceros, like Tajpirus and Equus, has a diffuse, non-deci- 

 duate placenta, I should have no hesitation in regarding Hyrax 

 as the type of a distinct order of deciduate Monodelphous Mam- 

 malia, Hyrax, in fact, hangs by Rhinoceros mainly by the 

 pattern of its molar teeth, — a character which affords anything 

 but a safe guide to affinity in many cases, t 



Concerning the placentation of the Sirenia we have no in- 

 formation. 



Among the Edentata, the Sloths have presented a cotyledonary 

 placenta, and the Armadillos have been affirmed to possess a 

 discoidal one. I am not aware that the minute structure of the 

 placenta has been examined in either of these groups, but I am 



* Home's description of the foetal membranes of the Tapir is very poor, but 

 Bauer's beautiful figures show clearly that the villi are diffuse, as in the Horse. 



f See, in reference to this point, the late Professor A. Wagner's excellent remarks 

 on Cuvier's exaggeration of the Ehinocerotic affinities of Hyrax, in Schreber's 

 " Saugethiere." Supp. Band, Abtli. iv. p. 307. 



