18/3.] DR. J. E. GRAY ON THE GENERA OF TURTLES. 395 



2. Notes on the Genera of Turtles (Oiacopodes) , and especi- 

 ally on their Skeletons and Skulls. By Dr. J. E. Gray, 

 F.R.S. &c. 



[Eeceived February 19, 1873.] 



The number of species of Turtles is very limited, which is the case 

 with the other sea animals that inhabit the warm or subtropical 

 regions of the ocean. The Turtles, like the Sperm-Whale, have an 

 extended geographical distribution, because many specimens wander 

 or are carried away by currents from their natural habitats, and are 

 often found as stragglers far away from the place which they pro- 

 perly inhabit. Thus the Luth (Sphargis) has been observed "in the 

 Mediterranean, and on the coast of Dorsetshire and Yorkshire, at 

 New Zealand, Australia, and on the coast of Japan ; but I have no 

 authority for believing that it breeds in any of these places. The 

 Loggerhead (Caouana), the imbricate Turtle {Caretta), and the 

 Turtle (Ckelonia) have also been found, under similar circumstances, 

 at a considerable distance to the north or south of the tropics. 



The species have been very imperfectly studied ; and several are 

 named in different works that are very insufficiently characterized, 

 and for this reason difficult to recognize as distinct. Four kinds 

 are recognized by sailors and the world in general ; and each of 

 these kinds has such a distinct organization as to be considered by 

 zoologists the type of a particular group ; but the characters of the 

 groups have been very imperfectly described. They each have a very 

 peculiar conformation of the head and skull ; these peculiarities have 

 not yet been used "by zoologists in the manner which they deserve. 



The Turtles or Oiacopodes, though they have a general external 

 resemblance, may be divided into two very distinct series. 



Several species are described, and said to be figured by Mr. Girard 

 in the ' Herp. Expl. Exped.' of Wilkes ; but our copy of that work 

 does not contain the plates, and the descriptions are very difficult to 

 understand*. 



* In reply to an inquiry about the imperfections in our copy of this work 

 to Prof. S. F. Baird, he states, " I have made an examination of our copy of 

 the plates of the Herpetology of the Exploring Expedition, and find it contains 

 the full number of thirty-two plates, corresponding to the explanations of the 

 plates. The Government edition of this work, and that which you have in the 

 British Museum, embraced only twenty-three plates, the additional ones having 

 been prepared at Mr. Girard's expense for the extra copies. 



" Should you desire this work, you can obtain it without any difficulty from 

 Messrs. J. B. Lippincott & Co. of Philadelphia, who published the book and 

 still have it on sale." — April 5th, 1873. 



P.S. (July loth). — The Society having lately received the Atlas of the ' Her- 

 petology of the TJ. S. E. E.' with 32 plates, I send the following notes on the 

 plates : — 



1. PI. 29. Thalassochelys corticata is Caouana caretta. 



2. PI. 30. f. 1-7. Caretta squamosa. Sooloo Seas. 



3. PI. 30. f. 8-13. Caretta rostrata. Fiji Islands. 



These two species are unknown to me ; but they are said to have imbricate 

 shields, and therefore cannot be Onychochelys kraussii. 



4. PI. 31. f. 5-7. Chelonia marmorata (not Euchelys macropus, as marked in 

 the plate). 



