128 BRITISH FOSSIL REPTILES. 



it is represented magnified at a and b. There is a linear series of small nervo- 

 vascular foramina a little below the alveolar border. The crowns of the developed 

 teeth have been broken away ; their fangs in the sockets are shown in fig. 7 ; the 

 anterior teeth are narrower than the rest, as in the upper jaw. On the inner side 

 of the specimen (fig. 8), a considerable extent of the symphysis {s, s) is shown. 



The posterior part of a broken dentary element of the left ramus is represented 

 in fig. 9, showing the last eight teeth, and the impressions of the crowns of as 

 many in advance. A portion of the crown, displaced, of the fourth from the last 

 is preserved, and likewise portions also of those in advance, which have been 

 broken in splitting the slab, so that they appear smaller than they actually were. 

 The last three teeth are entire, and show a gradual decrease of size, as in the 

 portion of upper jaw (fig. 4). A magnified view of the inner surface of the last 

 lower tooth is given at a, fig. 9. 



The reference of Echinodon to the Lacertians is suggested by its diminutive 

 size and by certain characters of jaws and teeth, but the structure of the vertebrae 

 and limb-bones must be ascertained before the ordinal afiinities of Echinodon can 

 be satisfactorily determined. The modifications of the mode of implantation of the 

 teeth in the known limits of the Dinosaurian order affect the value of the thecodont 

 character as a mark of affinity. 



