88 Dr. J. E. Gray on Trionyx Phayrei. 



five are visible and granular," -u'liich I suppose means the 

 nine bones of which the sternum of all Trionyces or mud- 

 tortoises (and, indeed, of all Testudinata) is formed : thus he 

 does not seem to be aware that what he calls the abdo- 

 minal plates are each formed of two bones, as he may see if 

 he will only consult Cuvier on the osteology of tortoises, in 

 his ' Ossemens Fossiles,' vol. v. p. 204. He goes on to de- 

 scribe the odd osseous plate as " semicircular, 7" 5'" along the 

 curve, and 1" 3'" in diameter in the mesial line ; anteriorly in 

 contact with tKe anterior pair, and posteriorly with the abdo- 

 minal ones," — a very important observation ; for, as Cuvier 

 observes, Geoffroy describes the sternum as composed of nine 

 bones, of which eight are in pairs and the ninth is odd and 

 placed constantly between the four anterior ones, with the 

 first two of which it adheres in preference when it is not 

 attached to the four. Then follows : — " The greatest length of 

 the abdominal plates is 8" ; they enclose an hourglass-shaped 

 cartilaginous area, the anterior portion being the largest, and 

 measuring 4" 3"' in diameter and 6" 8"' in length from the pos- 

 terior contraction to the odd plate." Thus you either only have 

 the general character of the order or the measurements of parts 

 and the shape of parts, as the cartilaginous area of the sternum, 

 given as the character of the species, which are liable to vary 

 in the different stages of growth of the same specimen. 



It would have been very useful if Dr. Anderson, instead of 

 criticising the works of other naturalists, and altering the 

 names because they are not in accordance with his idea of 

 euphony, aiid describing individual specimens as v^pccies, had 

 studied the changes that occur in the sternal callosities, the 

 dorsal disk, and other variations that do take place in the 

 growth of the Trionyces^ which has made them so difficidt to 

 understand by European naturalists who have had but a few 

 specimens in the museums to examine, but which at great 

 labour I have attempted in my various papers to imravel ; 

 for he lives in a country whore certainly some species of 

 the genus are abundant, and where they are to be ob- 

 tained in the markets, or certainly from the fishermen, with 

 very little labour ; and it Avould be very useful if a person 

 having such advantages would controvert or confirm the ob- 

 servations 1 have made. Had he jnnsued such a study, which 

 is quite consistent with the post he occupies, I am certain he 

 would not have confounded his specimen (which is, as I say, a 

 Landeniania, according to my division of the family) with the 

 Trionyx Phayrei of Theobald, which is most probably an As- 

 2^ilus or Dogania. And I consider such observations of far 

 greater importance to science than determining whether the 



