32 MR. EDWARD DEGEX OX THE 



the Balearic Islands. Though unquestionably more pyramido- 

 cephalous in regard to its supei'structure, it nevertheless holds a 

 position somewhat intermediate between L. jacksoni and some 

 of the more pronounced pyramidocephalous forms in this group 

 in regard to this particular feature. 



The variety lilfordi also shows the same exclusive pillar arrange- 

 ment of the processus ascendens for sole supjDort of the parietal 

 roof, which is so prominent a feature also in all the larger foiins 

 of Lizards from the Atlantic Islands such as L, sivionyi, gaUoti, 

 atlanticcij and also L. dugesii * (except in regard, to a modification 

 in the basal portions of the parietal process), all differing by having 

 pterygoid teeth, and all of which, except the latter, have strongly 

 ossiiied temporal regions. These dermal ossifications in Lacerta 

 jacksoni, as may have been seen, are present in a rudimentary 

 state in two of the supratemporal scutes. Specimens of Lacerta 

 viridis, agilis, and kevis may be quoted as further examples of 

 characteristic forms in which the postfrontals are single plates, 

 with perfectly analogous conditions in the relations between 

 parietal and supraoccipital. 



Also Lacerta ecMnata, from West Africa (except for its more 

 elongate skull), in which the processus ascendens, typically pyra- 

 midal, does not enter into direct contact with the parietal, but is 

 actually separated from it by confluence of the foraminpe retro- 

 frontalia. 



But it is the shape of the nasal process of the pr?emaxillary 

 perhaps, as previously remarked on in the male, which may 

 also provide a likely indication of closer affinity with some of 

 the Lizards of the Canary Islands and the European species of 

 Lacerta, viz. ocellata, viridis, and agilis — a character in which the 

 Balearic variety lilfordi does not share, being distinguished by a 

 narrower and very slender nasal process. 



So far as the topography of the skull reveals phylogenetic 

 affinity, it would appear that Lacerta jacksoni came from a 

 Palfearctic stock, but also exhibits special relationships betw^een 

 the West African and Atlantic Island forms. 



Remarks on Characters of Lepidosis in Lacerta jacksoni. 



Dimensions. — In regard to size, five specimens, all of them 

 males, are larger than the type of the species ; the two biggest 

 measuring 86 mm. from snout to vent, and consequently of 

 about the same length as is the largest of the males of Dr. 

 Peracca's series (consisting of seven specimens also), the length 

 of which is given as 85"5 mm. 



The male specimen, from which the skull was prepared for the 



* Siebenrock {vide I. c. p. 36) includes this species amongst those having divided 

 postfrontals. The specimens at my disposal, from the British Museum Collections, 

 show them distinctly to be single plates, with no indication of former sutures. 



