256 CLASS xv. 



conical nail. These nails or spurs (calcaria) are observed, near the 

 anus, in front of the commencement of the tail, in the genera Boa, 

 Python, Eryx and Tortrix. This bony apparatus is moved by its own 

 proper muscles. In other serpents there is only the first elongated 

 bone present beneath the skin, as in Amphisbcena and Typhlops. 

 In most serpents this apparatus is wanting altogether. See MAYER 

 Ueber die hintere Extremitdt der Ophidier, Nov. Act. Acad. Goes. 

 Leop. Carol. Tom. xn. p. 818 and foil. 



Through the absence of feet the serpents are restricted to creeping, 

 and for this purpose, according to the observations of BANKS and 

 HOME, they avail themselves of their numerous ribs, the extremities 

 of which they alternately fix on the ground and slide forwards, just 

 as caterpillars and myriapods deal with their feet. Philos. Transact. 

 for 1812, p. 163 sqq. 



Most serpents keep by preference in moist places, and within the 

 tropics shew themselves chiefly in the rainy season. In this order 

 very large animals are met with, which attain a length of 20 or 30 

 feet 1 , and on the other hand species also which are scarcely a span 

 long. 



Compare on this order PATRICK RUSSELL, An account of Indian Ser- 

 pents, collected on the coast of Coromandel, London, 1 796, fol. Continuation, 

 London, 1801 ; F. BOIE JSemerkungen uber MERREM'S Versuch eines Systems 

 der Amphibien. ErsleLieferung; Ophidier in OKEN'S Isis 1827, s. 508 566; 

 H. SCHLEGEL Essai sur la Physionomie des Serpens, La Haye, 1837, 8vo, et 

 Atlas contenant 1 1 planches et 3 cartes. SCHLEGEL'S work has been translated 

 (abridged) into English, see p. 234. Here may be added, on the habits of the 

 serpents of Germany, the prolix work of H. O. LENZ Schlangenkunde. Mit 

 Abb. Gotha, 1832, 8vo, containing many of his own observations. The most 

 recent arrangement of DDMRIL and BIBRON (Erpe"tologie, Tom. vi. vn.) 

 founded on the disposition of the teeth, is given in a succinct revision by 

 the former in the xxm. Vol. of the Mem. de I' Acad. des Sciences, 1853. It 

 need scarcely to be mentioned that exclusive attention to this point has 

 occasioned artificial genera and arbitrary separations or combinations. 



TRIBE I. Serpentes. 



Tongue bifid, exsertile. Lower jaw divided in the middle. 

 A. Eurystomi. 



Palate-bones mobile, armed with sharp, recurved teeth. Quad- 

 rate bone mobile, suspended to the mastoid bone, itself mobile, 



1 ADANSON speaks of serpents 40 or 50 feet long, which however were not seen by 

 himself. Hist. nat. du Senegal, p. 150. 



