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Show 1873.] DR. J. E. GRAY ON THE GENERA OF TURTLES. 395 2. Notes on the Genera of Turtles (Oiacopodes), and especially on their Skeletons and Skulls. By Dr. J. E. GRAY, F.R.S. &c. [Received February 19, 1873.] The number of species of Turtles is very limited, which is the case with tbe 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 properly 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 ( Chelonia) 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, be states, " I have made an examination of our copy of the plates of the Herpetology of tbe 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 15th).-The Society having lately received the Atlas of the 'Herpetology of the TJ. S. E. E.' with 32 plates, I send the following notes on the plates:- 1. Pl. 29. Thalassochelys corticate is Caouana caretta. 2. Pl. 30. f. 1-7. Caretta squamosa. Sooloo Seas. 3. Pl. 30. f. 8-13. Caretta rostrata. Fiji Islands. These two species are unknown to m e ; but they are said to have imbricate shields, and therefore cannot be Onychochelys kraussii. 4. Pl. 31. f. 5-7. Chelonia marmorata (not Euchc/ys macropus, as marked in the plate). |