2448 TORTOISES, TURTLES, AND PLESIOSAURS 



an additional (mesoplastral) pair between the normal hyoplastral and hypo- 

 plastral bones. 



The side-necked tortoises, of which the great majority may be included in 

 the two families mentioned above, are all of fresh- water habits, and at the pres- 

 ent day are exclusively restricted to the Southern Hemisphere, while they are the 

 only members of the order found in Australia and New Guinea. During the earlier 

 portion of the Tertiary period they extended, however, into the Northern Hemis- 

 phere, and in the preceding Secondary period were abundantly represented in 

 Europe. These facts show that the group is a very ancient one; and by the 

 presence of the additional mesoplastral elements in the lower half of the shell of 

 some of its representatives it is allied to a third and totally extinct group, which 

 disappeared before the close of the Secondary period. 



The extraordinary reptile depicted in the following illustration, 

 and known as the matamata {Cheyls fimbriata], is the typical repre- 

 sentative of the first of the existing families of the group Chelyidce. 

 The various genera included therein are collectively characterized by having the 

 normal nine bones in the plastron, by the neck being incapable of complete retrac- 

 tion within the margins of the shell, and the absence of a bony temporal arch to the 

 skull. Eight genera are included in the family, the range of which is restricted to 

 South America, Australia, and New Guinea. 



The matamata, which is an American species inhabiting Guiana and Northern 

 Brazil, and is the sole representative of its genus, is easily recognized by its broad 

 and elongated neck, of which the sides are fringed with peculiar fimbriated projec- 

 tions, and the depressed and triangular head terminating in a proboscis-like nose, 

 and furnished with very small eyes. Not less characteristic is the equally de- 

 pressed and much corrugated shell, in which the carapace bears three longitudinal 

 ridges, subdivided into nodose protuberances by cross valleys; the horny shields of 

 the same being extremely rugose, and marked with deep radiating striae. The ver- 

 tebral shields are broader than long, and the hinder marginals are more or less 

 strongly serrated, while there is a distinct nuchal shield on the front edge of the car- 

 apace. On the removal of the horny shields from the carapace, it is seen that only 

 the last pair of costal bones meet in the middle line, owing to the presence of but 

 seven neural bones. The plastron is narrow and deeply notched behind, the tail is 

 very short, and the toes are fully webbed. In addition to the rows of fimbriated 

 appendages on each side of the neck, there is a similar outgrowth of skin on the 

 chin and larger pair of appendages above the ears. In color the adult is uniform 

 brown, but the young are prettily marked with bands of brown and yellow on the 

 chin and neck, while the shell is ornamented with black and yellow spots. The 

 species is of comparatively-large size, the shell attaining a length of fifteen inches. 



Unfortunately, but little is known as to the mode of life of this strange tortoise. 

 When in its native element, the wart}'- appendages on the neck float in the water 

 like some vegetable growth, while the rugged and bossed shell strongly resemb 1 es 

 a stone; and it is thus probable that the whole appearance of the creature is advan- 

 tageous either in deluding its enemies or in attracting to it the animals on which it 

 feeds the latter being the more likely hypothesis. Although it appears that the 



