196 ZOOLOGY, 
uortli of Mexico. The lower forms of turtles are the ma- 
rine species. Such is the great sea-turtle {Sphargis cori- 
acea) of the Atlantic and Mediterranean, which is the larg- 
FiG. 239.— Skeleton of European Tortoise, with the plastron or under shell 
removed. 
est of all existing turtles, and is sometimes eight feet long, 
weighing from eight hundred to twelve hundred pounds. 
Next to this species is the loggerhead turtle {Thalassochelys 
caouana), which is sometimes seen asleep in mid- ocean. 
