THE SIDE-NECKED TORTOISES 2453 



being olive above and yellow beneath, with some yellow spots on the head. All 

 the other members of the genus are of greatly inferior dimensions; a second Ama- 

 zonian species (P. sextuberculata) , having a shell of scarcely more than a foot in 

 length, and being distinguished from its larger relative by the. presence of only a 

 single wattle on the chin. 



The best account of the habits of these tortoises is the one given by Humboldt, 

 who speaks of the large species by its native name of arran. On the Orinoco, ac- 

 cording to this account, the period of egg laying coincides with that of the lowest 

 Tevel of the waters of the river, or from the end of January till the latter part of 

 March. During January the tortoises collect in troops, which soon leave the water 

 to bask on the warm banks of sand exposed by the lowering of the river. Through- 

 out February they may be found on such banks during the greater part of the day; 

 but early in March the several troops collect in larger bodies, and then make their 

 way to the comparatively -few islands where the eggs are habitually deposited. At 

 this time, shortly before the egg laying commences, thousands of the tortoises may 

 be seen arranged in long strings around the shores of the islands in question, 

 stretching out their necks, and holding their necks above water, in order to see 

 whether there is anything to prevent their landing in safety. As the creatures are 

 exceedingly timid, and especially averse to the presence of human beings or boats, 

 the Indians, to whom the harvest of tortoise eggs is of the utmost importance, take 

 every precaution to prevent them being disturbed, posting sentinels at intervals 

 along the banks, and warning all passing boats to keep in the middle of the river. 

 When the tortoises have landed, the laying of the eggs takes place at night, and 

 begins soon after sunset; the females digging holes of some three feet in diameter 

 and two feet in depth, by the aid of their powerful hind-limbs. So great is the 

 contention for space, that one tortoise will frequently make use of a pit dug by a 

 neighbor, and in which one set of eggs has already been deposited, although not 

 yet covered over with sand, two layers of eggs thus occupying one area. The 

 crowding and jostling of the reptiles necessarily leads to an immense number of eggs 

 being broken, which is estimated at a fifth of the whole; the contents of the frac- 

 tured shells in many places cementing the loose sand into a coherent mass. The 

 number of tortoises on the shore during the night being so large, many of them are 

 unable to complete the work of egg laying before dawn, and these belated individ- 

 uals become quite insensible to danger, continuing there even in the presence of the 

 Indians, who repair to the spot at an early hour. 



The great assemblage of these Chelonians takes place on one particular island 

 in the Orinoco, hence known as the Boca de la Tortuga, and according to native 

 accounts, no other spot is to be met with on the river from its mouth to its junction 

 with the Apure, where eggs can be found in abundance. On the island in question, 

 the number of eggs deposited is enormous, a large stretch of smooth sandy beach 

 being underlain with an almost continuous layer. To determine the position and 

 extent of the deposit, a long pole is thrust down at intervals into the sand; the sud- 

 den want of resistance to its descent proclaiming when the loose layer containing 

 the eggs has been reached. According to measurements taken by Humboldt, the 

 stratum extended to a distance of one hundred and twenty feet from the water, and 



