Causes which retard Zoological Knowledge. 305 



ing similar, they naturally arrange themselves under one genus, 

 but admit of being divided into two sections. 



Mr. Say had confounded the Testudo scabra of Linn., which 

 inhabits South America, with a kindred species existing in New 

 Jersey, in the vicinity of Philadelphia. This species was subse- 

 quently described as distinct by Major Le Conte, under the name 

 of Emys inscripta. Mr. Gray has unnecessarily increased the 

 synonyma by adding the specific appellation of " speciosa^^ to this 

 tortoise. (Vide p. 26.) 



The Emys concentrica, or centrata, is the only tortoise vulgarly 

 called Terrapin in our country; it has been so long and so high- 

 ly esteemed as a luxurious article of diet with us, as to have oc- 

 casioned the almost total extinction of the species in the vicinity 

 of Philadelphia ; but the Emys serrata, or red-bellied terrapin, — 

 E. rubriventris of Le Conte, is beginning to appear in our market 

 to replace it in some degree ; the former have been sold for six 

 dollars a dozen, and are brought from a distance of more than a 

 hundred miles: we have seen a black-spotted variety of this 

 species from South Carolina. 



The Emys vittata of Gray, is very probably the young of the 

 E. concinna of Le Conte. — Vide Cuv. Regne Anim. 



E. decussata, E. rugosa, and E. scripta, of Gray, are mere vari- 

 eties of E. serrata, (Daudin,) which is very common in our middle 

 and southern states. 



The E. Lesueuri, (Gray,) has been more descriptively named 

 E. geographica by Lesueur himself; writers cannot too scrupu- 

 lously avoid adding to the already plethoric list of synonyma. 



E. Bella, E. Kinosternoides, and E. Annulifera, of Gray, do not 

 appear as yet specifically identified. Vide pp. 31, 32. 



In two of our fresh water tortoises, viz. E. odorata and E. pen- 

 syhanica, the anterior and posterior lobes of the sternum, are 

 frequently united to the middle lobe by a cartilaginous suture 

 only, admitting of slight motion ; a peculiarity which was thought 

 sufficiently important by Spix, on which to construct a new ge- 

 nus, under the name of Kinosternon, an arrangement adopted 

 by Bell and Gray, although it is admitted that these sutures are 

 liable to become obliterated by age ; under which circumstance, 

 an old individual of E. odorata was pronounced a distinct species 

 by Daudin and Merrem, and named " Glutinata /" 



The fourth genus, Chelydra, of Schweiger, also constructed 

 Vol. L— 39 



