ANATOMY OF VERTEBRATES. 153 



rior and upper part- of the maxillary is smaller and convex. Tlie 

 maxillary l)()ne is pushed h>rward and rotated upon the lacrymal 

 joint by the advance of the ectopterygoid, which is associated with 

 the movements of the tympanic pedicle of the lower jaw by means 

 of the true pterygoid bone. The premaxillary is edentulous. A 

 long, perforated poison-fang is anchylosed to the maxillary. The 

 palatine bone has four or five, and the pterygoid from eight to ten, 

 small, imperforate, pointed, and recurved teeth. The frontal bones 

 are broader than they are long : there are no superf)rbitals. A strong- 

 ridge is developed from the under surface of the basisphcnoid, and 

 a long and strong recurved spine from that of the l;)asioccipital ; 

 these give insertion to the powerful ' longi colli ' muscles, by which 

 the downward stroke of the head is performed in the inflicti(m of 

 the wound by the poison-fangs. 



The skull of the ty])lcal Ophidian reptiles most resembles that 

 of Lizards, biit lacks the outer diverging appendage, formed by the 

 malar and squamosal, ut the maxillary arch. It differs from that 

 of Batrachians in the distinct basi- and superoccipitals ; in the 

 superoccipital forming part of the car-clianil5er ; in tlie liasioc- 

 cipital combining with the exoccipital to form a single articular 

 condyle for the atlas ; in the ossification of the membranous space 

 between the elongated parietals and the s]ilienoid; in the constant 

 coalescence of the parietals with one another ; in the connation of 

 the orbitosphenoids with the fVontals, and in the meeting of the 

 orbitosphenoids below the prosencephalon upon the upper sur- 

 face of the presphenoid ; in the presence of distinct postfrontals, 

 and the attachment thereto of the ectopterygoids, whereby they 

 form an anterior point of suspension of the lower jaw, through the 

 medium of the pterygoid and tympanic Ijones ; in the connation 

 of the prefrontal? and lacrymals. 



In the Amj^liisbccna fulii/inosa coalescence still further simplifies 

 the cranial structure : the parts of the epencephalic arch con- 

 stitute a single occipital bone ; the superoccipital crest extends 

 forward into a sagittal one ; a small foramen marks the boundary : 

 the premaxillary is single, and, with the rest of the upper jaw, is 

 fixed ; the tympanic is short, compared with that of true Serpents, 

 and extends almost horizontally forward, in a line with the lower 

 jaw which it supports; the coronoid is more developed. The 

 nostrils, divided by the premaxillary, are terminal ; or even, as 

 in Lepldosternon, may open behind the fjre end of the skull : in 

 this Amphisba3nian the maxillaries overlap the nasals to join the 

 premaxillary. ^ 



' CLXXIII., pi. 15, figs. 8, 11. 



