THE EDENTATA ENTOMOPHAGA. 335 



The teeth are five in number on each side above, and 

 four below, and become sharpened by mutual attrition into 

 a chisel-like form. The stomach is remarkably complex. 



The Gravigrada are, for the most part, like the Sloths, 

 South American forms, but they are entirely extinct ; and 

 while, in most respects, they resemble the Sloths, in others 

 they present an approximation to Ant-eaters. 



The jugal arch may be complete or incomplete. The 

 articular surfaces of the dorsal vertebrse are sometimes 

 complicated in a manner similar to that observed in the 

 Ant-eaters. The tail is very long and strong. The limbs 

 are short and sub-equal, whUe the fore foot has the ulnar 

 digit imperfect, as in the Ant-eaters. The fibula has 

 no inward process, and the astragalus is consequently de- 

 void of any fossa upon its outer surface. But another 

 kind of peg and socket ankle-joint is produced by the 

 interlocking of the surfaces of the tibia and of the astra- 

 galus. 



The great extinct animals. Megatherium, Mylodon, Me- 

 galouyx, &c., the remains of which have been found almost 

 wholly in later tertiary deposits of America, belong to this 

 group. 



2, The Entomophaga. — In this group of Edentata the zy- 

 goma sends down no process from its lateral region, 

 although, in some rare cases, the anterior part of the arch 

 has a descending prolongation. The acromion and the 

 coracoid do not become united. The scaphoid and the 

 trapezium remain distinct ; and the sole of the hind foot 

 rests upon the ground by a greater or lesser extent of its 

 whole surface, and not merely by its outer edge. 



The insectivorous edentates are divisible into four groups 

 — a. the Mutica, b. the Squamata, c. the Tubulidentata, and 

 d. the Loricata. 



a. The group of the Mutica contains the genera Myrme- 

 cophaga and Cyclothurus, the Ant-eaters of South America. 

 The bodies of these animals are covered with hair, and they 

 are provided with very long tails, which are sometimes pre- 

 hensile. The skull is greatly elongated, and the small pre- 



