Genus Crotal**. 



640. The skeleton of the Rattlesnake (Cntalu* Jomoto). ' 



It HMMVW4 feet 4 inches in length, and includes 194 vertebra?, of which 168 mpport 

 saoveaMe rib* : the number of uil-rrrtehna ii 25, bat the anchylosed terminal one* which 

 support the rattle are wanting in this skeleton. All the abdominal rertebne hare hypapo- 

 physes, equalling iu length the neural spines, and a short proceaf esteoda outwards above Uir 

 articular surface of the diapophysis and below that of the anterior zygapophysis. The hyp- 

 pophrtu of the basiocciphal is single, and appean to terminate the strong ridge developed 

 from the under part of the basbpbenoid : the maxillary bone* are short, subcubical, deepl) 

 excavated externally, and tnpporting one long, curved, perforated poison-fang which i 

 anchyloted to the bone : behind this are sereral loose rudiments of soccetakmal fangt. Tin 

 external ridge of the coronoid depression of the under jaw is almost obsolete, the process for 

 the implantation of the temporal muscles being formed exclusively by the internal ridge. 



MM. South 



641. The skull of a Rattlesnake (Crotaltu durum*), which shows well the typical 

 characters of that part of the skeleton of a poisonous snake. 



Theae character! consist chiefly in the modification of form and attachments of the supe- 

 rior maxillary bone, which is moreably articulated to the palatine, ectopterygoid and lachry- 

 mal bones ; bat chiefly supported by the latter, which presents the form of a short, strong, 

 three sided pedicle, extending from the anterior external angle of the frontal to the anterior 

 and upper part of the maxillary. The articular surface of the maxillary is slightly concave, 

 of an oral shape t the surface articulating with the ectopterygoid on the posterior and upper 

 part of the maxillary is smaller and convex. The maxillary bone is pushed forward and 

 routed upon the lachrymal joint by the advance of the ectopterygoids, which are associated 

 with the morements of the tympanic pedicle of the lower jaw by means of the true pterygoid 

 bones. The premaxillary bone is edentulous. A single, long, perforated poison-fang is anchy 

 lossd to the right maxillary, and two similar fang* to the left maxillary, in the present speci 

 men. The palatine bones have four or five, and the pterygoids from eight to ten, small, im- 

 perforate, pointed and recurved teeth. The frontal bones are broader than they are long 

 there are no superorbitals. A strong ridge is developed from the under surface of the basi- 

 sphmnid, sad a long and strong recurved spine from that of thr basiocripital ; these give in- 

 sertion to the powerful ' longicolli ' muscles, by which the downward stroke of the head i* 

 performed in the infliction of the wound by the poison-fugs. 



Pretented by Prof. Owen, F.R.S. 



642. A chain of vertebrae of the Rattlesnake (Crotalu* horrid**), wanting the ribs. 



The hypapophytu, which is developed from the anterior vertebra: only in moat Serpent*, 

 is here present on all the abdominal vertebra;. A short process extends downwards and for- 



