Classification of the Mammalia. 57 



larger species are frugivorous and have corresponding; modifica- 

 tions of teeth and stomach. The mammae are pectoral in posi- 

 tion, and the penis is pendulous in all Cheiroptera. The most 

 remarkable examples of periodically torpid Mammals are to be 

 found in the terrestrial and volant Insectivora. The frugivorous 

 Bats differ much in dentition from the true Cheiroptera, and would 

 seem to conduct through the Colugos or Flying Lemurs, directly 

 to the Quadrumanous order. The Cheiroptera are cosmopolitan- 



The order Bruta, called Edentata by Cuvier, includes two 

 genera which are devoid of teeth ; the rest possess those organs, 

 which, however, have no true enamel, are never displaced by a 

 second series, and are very rarely implanted in the premaxillary 

 bones. All the species have very long and strong claws. The 

 ischium as well as the ilium unites with the sacrum ; the orbit 

 is not divided from the temporal fossa. I have already adverted 

 to the illustration of affinity to the oviparous Vertebrata which 

 the Three-toed Sloths afford by the supernumerary cervical verte- 

 brae supporting false ribs and by the convolution of the windpipe 

 in the thorax ; and I may add that the unusual number — three 

 and twenty pairs — of ribs, forming a very long dorsal, with a short 

 lumbar region of the spine in the Two-toed Sloth, recalls a lacer- 

 tine structure. The same tendency to an inferior type is shown 

 by the abdominal testes, the single cloacal outlet, the low cerebral 

 development, the absence of medullary canals in the long bones 

 in the Sloths, and by the great tenacity of life and long-enduring 

 irritability of the muscular fibre, in both the Sloths and Ant- 

 eaters. 



The order Bruta is but scantily represented at the present 

 period. One genus, Manis or Pangolin, is common to Asia and 

 Africa ; the Orycieropus is peculiar to South Africa ; the rest of 

 the order, consisting of the genera Myrmecophaya, or true Ant- 

 eaters, Dasypus or Armadillos, and Bradypus or Sloths, are con- 

 fined to South America. 



Gyrencephala. 



In next proceeding to consider the subdivisions of the Gyren- 

 cephala, we seem at first to descend in the scale in meeting with 

 a group of animals in that subclass, having the form of Fishes ; 

 but a high grade of mammalian organization is masked beneath 

 this form. The Gyrencephala are primarily subdivided, according 

 to modifications of the locomotive organs, into three series, for 



