Oi? THE CLASS MAMMALIA. 23 



The order Cheiroptera, with the exception of the modification 

 of their digits for supporting the large webs that serve as wings, 

 repeat the chief characters of the Insectivora ; but a few of the 

 larger species are frugivorous and have corresponding modifica- 

 tions of the teeth and stomach. The mamma? are pectoral in 

 position, 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 

 woidd seem to conduct through the Colugos or Flying Lemurs, 

 directly to the Quadrumanous order. The Cheiroptera are cos- 

 mopolitan. 



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 vertebrae 

 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 Orycteropus is peculiar to South Africa ; the rest of 



* This latter vital character attracted the notice of the earliest observers of 

 these animals. Thus Marcgrave and Piso narrate of the Sloth : — " Cor motum 

 suum validissime retinebat, postquam exeniptum erat e corpore per semiho- 

 rium : — exempto corde cseteris visceribus, multd post se niovebat et pedes lente 

 contrahebat sicut dormituriens solet." Buffon, who quotes the above from the 

 ' Historia Naturalis Brasilia?,' p. 322, well remarks, " Par ces rapports, ce 

 quadrupede se rapproche non seulement de la tortue, dont il a la lenteur, mais 

 encore des autres reptiles et de tous ceux qui n'ont pas un centre du sentiment 

 unique et bicn distinct." — Hist. Naturelle, 4to, torn. xiii. p. 45. 



