306 Causes which retard Zoological Knowledge, 



on the old genus Emys, possesses stronger claims to distinction> 

 though we at the same time prefer the more classic name ^' Che- 

 LONURA," of Dr. Fleming, for this genus : it consists, according 

 to Mr. Gray, of only a single species, vulgarly called alligator- 

 tortoise, or " snapping-tortoise," of the middle states, and known 

 to the African slaves of the southern states by the name of 

 " couta," probably from some fancied resemblance to an animal 

 of their own country. We have, however, seen the shells of three 

 other distinct species of this genus ; one from our northern lakes, 

 one from South America, and another from oriental India, from 

 the river Silet, a branch of the Burrempootra. 



The family " trionychid.^:," includes a very interesting group 

 of fresh water tortoises : two or three species having been re- 

 cently observed with more than three claws ; the genus trionyx, 

 will not, as heretofore, include all the species. — Mr. Gray's re- 

 marks on the species of this genus would be more useful, had he 

 stated the dimensions, in his descriptions of animals varying in 

 size, from a few inches, to a foot, and more. 



The remarks of our author on the sea tortoises, (family chelo- 

 NiADCE,) are not without interest ; his first genus, sphargis, of 

 Merrem, has been better named " cortudo," by Fleming. — Vide 

 Philosophy of Zoology. — These animals attain to a great size oc- 

 casionally on our coasts, as noble specimens preserved in our mu- 

 seums abundantly testify. An individual now in the New York 

 museum, purchased by the proprietor for 8500, was thrown on 

 the coast of Long Island, in a recent N. E. gale, and weighed 

 1400lbs. Mr. Gray gives as the habitat of this species, " in mare 

 Mediterraneo." 



In the second order, — or emydosauri, of Blainville, are ar- 

 ranged all the living crocodiles and alligators. We think the 

 denomination of crocodilini, applied by Oppel to this group, pre- 

 ferable on many accounts. Alluding to the general characters 

 of this group, Mr. Gray repeats the exploded error, relative to a 

 very important point in their anatomy : viz. " the heart is three 

 celled," &c. — Vid. p. 55. — This oversight is the less excusable in 

 Mr. G. inasmuch as he quotes the book, in which correct infor- • 

 mation is contained relative to this subject. 



The habits which our author attributes to the animals of this 

 group, will not apply in any respect to our alligator, which feeds 

 chiefly on live fish. (Vid. Bartram's Travels, et passim.) We re- 



