REPTIL1A. 



273 



connected together by very perfectly con- 

 structed ball and socket joints, each vertebra 

 presenting a concavity in front, and a convex 

 ball upon its posterior aspect ; the plane of 

 the circumference of the articulating surface 

 being oblique from before to behind. 



The spinous apophyses are generally elon- 

 gated and flattened, being prolonged poste- 

 riorly to the articular apophyses, which they 

 partially overlap. 



The articulating processes are of two sorts ; 

 some facing outwardly, represent ordinary ar- 

 ticulating apophyses, with horizontal facets. 

 The second face inwards, and are situated at 

 the base of the spinous process. These apo- 

 physes are so arranged, that, as in the lum- 

 bar vertebras of some Edentata amongst quad- 

 rupeds, two vertebra? are articulated toge- 

 ther by a double tenon received into a double 

 mortice, the only difference being, that the 

 facets of the upper tenon and mortice are 

 continuous, and form with each other an 

 acute angle. 



The articular facets, without including 

 those of the bodies, are twelve in number for 

 each vertebra; an arrangement which re- 

 stricts the vertical movements of the spine 

 very materially, whilst at the same time it 

 permits very free motion in a horizontal di- 

 rection. 



The transverse processes are very short 

 and scarcely perceptible, except by a tubercle, 

 which offers two facets for articulation with 

 the ribs. In the caudal vertebras, however, 

 the transverse processes are much longer, and 

 inclined downwards ; they are even double to- 

 wards the anterior part of the caudal region. 



In almost all serpents, the body of the ver- 

 tebras presents inferiorly a prominent longitu- 

 dinal crest, which very generally terminates 

 behind in a prominent spine, that is directed 

 more or less towards the tail. In some ge- 

 nera, as in Crotalus, for example, this spine is 

 even longer than the superior spinous process, 

 and moreover is very frequently double. 



The arrangement of the articular processes 

 described above is not met with in the genera 

 Anguis and Cecilia, in which it resembles what 

 is found in lizards; and in Amphistasna, Ery.r, 

 &c., traces, merely, of either superior or in- 

 ferior spinous processes can be detected. 



The ribs of serpents are enormously nume- 

 rous, their number varying, according to the 

 proportions of the species, from 51 pairs 

 (Sheltopmick), up to three hundred and twenty 

 pairs (Python}. Each pair of ribs is move- 

 ably articulated, by means of two slight con- 

 cave surfaces, with corresponding articulating 

 facets of the transverse processes of the cor- 

 responding vertebra, forming a kind of double 

 ball and socket joint, which allows of an un- 

 usual extent of motion. There is no vestige 

 of a sternal apparatus in any of the Ophi- 

 dian reptiles, but each rib terminates by a 

 single tapering cartilage, which is attached 

 by muscular connexions, to be described 

 hereafter, to the abdominal scuta of the inte- 

 gument. 



Myology of Chclonian Reptiles. In the 



VOL. IV, 



Chelonian reptiles*, the cervical portion of the 

 spine is composed of long and very moveable 

 vertebras, which form a curve, the concavity 

 of which is upwards, whilst the dorsal region 

 is converted into a broad immoveable shield 

 by the consolidation of the ribs and vertebrae : 

 there consequently cannot be any muscles of 

 the back, whilst those of the neck, on the 

 contrary, are very distinct; nevertheless, the 

 attachments which they necessarily have be- 

 neath the back and the ribs, instea'd of on the 

 outer side, as is usually the case, renders it 

 exceedingly difficult to compare them with 

 those of other animals. Still some points of 

 relationship may be traced between them and 

 those of birds. Thus, in the horizontal por- 

 tion of the neck, close to the bones, are the 

 inter transver sales, separable, as in birds, in- 

 to two sets of fasciculi, one upon the dorsal, 

 and the other upon the ventral aspect. These 

 are the intertransversarii colli and transversarii 

 colli obliqid of Bqjanus, 



There is, moreover, in this horizontal part 

 of the neck, the great transversalis, composed, 

 as in birds, of two fascicles inserted into the 

 transverse process of each vertebra, and de- 

 rived from the transverse processes of the 

 two preceding vertebrae. The anterior longus 

 colli arises from the first dorsal vertebra ; it 

 runs along all the ventral aspect of the curva- 

 ture of the neck, receiving additional fibres 

 from, and giving off tendons to all. 



Another muscle, very similar in its dis- 

 tribution to the longus colli posticus of birds, 

 but slightly different in its insertion, arises 

 from the carapax in front of the last vertebra 

 of the neck, and gives off fleshy fasciculi to 

 four or five of the vertebrae that precede it, 

 but it inserts them into the crests, which 

 represent spinous apophyses : moreover, 

 there is no accessory muscle as in birds. In 

 one circumstance, however, there is a re- 

 semblance, namely, its last fasciculus, which 

 is very long ; those likewise to the head, 

 where it is inserted into the upper aspect 

 of the head, above the splenius : neverthe- 

 less it is not digastric, as that of birds. The 

 larger portion of this muscle is named by 

 Bojanus the spinalis colli, and the slip which 

 it gives off to the head the splenius capitis : 

 the tortoise has also a small complexus, 

 which is derived only from the transverse 

 apophyses of two or three of the anterior 

 cervical vertebras, and runs to the head, ex- 

 ternal to the splenius and to the fasciculus 

 above mentioned. This splenius, which does 

 not exist in birds, arises in the land and fresh- 

 water tortoises from the dorsal crests of the 

 fourth, fifth, and sixth vertebras, and runs to 

 the head, where, dividing into two portions, 

 it covers the upper surface of the occiput : 

 this is the biventer cervicis of Bojanus. In 

 the turtles its divisions are more widely 

 separated ; the internal arises only from the 

 most anterior vertebra?, whilst the external is 

 derived from beneath the anterior edge of the 



* Cuvier, Lemons d'Anatomie Compare, last edi 

 tion. 



