TORTOISES. 7 



Among the fresh-water tortoises we should remark 



The Box Tortoises*, 



The sternum of which is divided by a moveable articulation into two lids, 

 which, when the head and limbs are withdrawn, completely encase the 

 animal in its shell. 



In some the anterior lid only is moveable"!". 

 In others both are equally so J. 



There are some fresh-water Tortoises, on the contrary, whose long tail 

 and voluminous members cannot be completely retracted within the shell. 

 These approximate, in this respect, to the following subgenera, and parti- 

 cularly to the Chelydes, and render them consequently worthy of dis- 

 tinction§ . Such is, 



Test, serpentina, L. ; Schcepf. pi. vi, (The Snapper), which may 

 be easily recognised by its tail, nearly as long as its shell, and bris- 

 tled with sharp and dentated crests, and by its pyramidically elevated 

 plates. It is found in the warm parts of North America, where it 

 destroys numbers of fishes and aquatic birds, wanders far from rivers, 

 and sometimes weighs upwards of twenty pounds. 



3. The Sea-Tortoises. — Chelonia||, Brongn. 



The envelope of the Sea Tortoises is too small to receive their head, 

 and particularly their feet, which are very long (the anterior ones most so), 

 and flattened into fins, whilst their toes are all closely united in the same 

 membrane. The two first ones of each foot being alone furnished with 

 pointed nails, one or other of which at a certain age is very often lost. 

 The pieces of their sternum do not form a continuous plate, but are va- 

 riously notched, leaving considerable intervals, which are filled with car- 

 tilage only. The ribs are narrowed and separated from each other :it 

 their external extremities; the circumference of the shell, however, is 

 surrounded with a circle of pieces corresponding to the ribs of the ster- 

 num. The temporal fossa is covered above by an arch formed by the pa- 

 rietal and other bones, so that the whole head is furnished with an unin- 

 terrupted osseous helmet. The internal surface of the oesophagus is 



fusca, Lesueur; — Em. leprosa, Schw. ; — Em. nasuta, Id.; — Em. dorsala, Schoepf. ; — 

 Em. pnlchella, Schoepf. XXVI, or inseulpta, Le Conte; — -Em. lutescens, Schw.; — Em. 

 expansa, Id.; — Em. Macquaria, Cuv. 



M. Fitzinger separates under the name of Chelodina, and M. Bell under that of 

 Hydraspis, those species which have a mure elongated neck, such as the Em. longi- 

 cotlis, Shaw, Gen. Zool. Ill, part I, pi. xvi; — Em. planiceps, Schoepf. XXVII, or ca- 

 naliculata, Spix, VIII; — Em. platicephala, Mcrrem; — Em. depressa, Spix, III, 2; — 

 Em. carunculata, Aug. St. Hil.; — Em. tritentaculata, Id. 



* This suhdivision gave Mcrrem his genus Terrapene, Spix his K inosternon, 

 and Fleming his Cistuda. The European species, and others, already partake of 

 this nioveahility, which renders the task of limiting the genus a difficult matter. 



t Test, subnigra, I, vii, 2; — T. clausa, Schoepf. VII. 



% La Tortue a boite d' Am boine, Daud. 11,309;— Test, tricarinata, Schoepf. II; 

 Test, pennsylvanica, I, d. xxiv. [To which may be added T.odorata, Daud.] 



§ This suhdivision has furnished M. Fitzinger with his genus Cheli de i,and M. 

 Fleming with that of Chelonura. 



|| ( helonia, from chelone. Merrem has preferred the barbarous nam "i C »retta. 



