2G6 



\'Ein'EBi;ATE ANIMALS. 



l)erio(lically shed along witli the rest c>f the external or epidermic 

 layer of the integument, and is again renewed. The p\ipil is round 

 in most serpents, but it forms a veitical slit or fissure in many ven- 

 omous Snakes and in the Boas. 



As regards the teeth, it is to be noticed that the snakes are not 

 in the habit of chewing their prey, but of swallowing it whole, and 

 tlie construction of their dental api>aratus is in accordance with this 

 ]ieculiarity. The l<jwer jaw, as before said, articulates with the 

 skull by means of a ijuadrate bone (tig. 185), and this in turn is 

 movably jointed to the cranium. The two h.alves of tlie lower jaw 

 are also merely' united loosely in front l.iy ligaments and muscles. In 

 conseijuence of this peculiar arrangement of [larts, the serpents have 

 the povrer of opening the mouth to an extraordinary width, and 

 they can perform the most astonishing feats in the way of swallow- 



Fi- l:il. — Skull (iltlic li;d(lcsii;iki> (.iftfiDHiiirvil uii(\ nihniii). ; I half nfllie lower 



j.-iw uiiit.'.l In till' sl;iill ti\-fIi(M|i(;iiIr,Hi- lintie{7) ; in Uppir jnw ciinyin^ tlic- poisoti- 

 nin- ; J. Series iil' t.'rt.h ll|i'JU the leil.lle. 



ing. The teeth are snii]iiy litted for seizing and In^lding the prey, 

 lint not in .my w.iy for chewing or dividing it. In the hannless 

 snakes till" ti-i'tli arc in the form of solid cones, M-hich are arranged in 

 rows loinid the wliolo of tlu' ujiper anil lower jaws, a donble row exist- 

 ing on t]\r |i;ila(e as well. In the venomous snake.s, on the other hand, 

 tlie- ordinary ti-etli ;irc usually wanting ujion the U]iper jaws, or are 

 few in nniiibri- ; and (liosi- bones .are themselves ULUch reilueed in 

 size. Tn jilace of the onlinary teeth, however, or in addition to 

 these, the U|iper jau's eariT llie sci-called " poiMiii-f.augs " (tig. ]!)!). 

 Jn the Yi|ierine Snal:es these aic ;t, ]);tii- of long eur\a'il fangs, one 

 on eaeh maxilla or upper jawlione, \\hieh, when not in use, are 

 pointed liaekx\ards, but eau be raised ;it will by speei:d nuiscles, by 

 the eli'valion of the movable niaxilhe. Kaeh tooth is jierfoi'ated by 

 a line eaiial or lulu-, whir'h opens by a clistbict aperture ,a,t the jioint 



