6 ME. G. A. BOULENGEE ON LIZAEDS 



2. The subject has been discussed in relation to Prof. v. Meliely's proposal to 

 reverse the series as I conceive it, and I liave appealed, in support of my contention, 

 to examples drawn from other groups of Vertebrates; my opinion is also based on 

 considerations derived from a study of Reptilian morphology in series which paleon- 

 tology conclusively shows' to have evolved in a definite direction. In the case of 

 Lacerta, the internarial bony space and the postfronto-squaTnosal arch are broader in 

 Tj. agilis than in any other member of the genus *. The osteodermal plates are most 

 reduced in the forms with strongly flattened skulls ; on the other hand, they increase 

 in development in L. viridis, ocellata, and galloti (in a different line of evolution), 

 in which a flattening of the head and an elongation of the snout obtain as in 

 Section IV., though to a less exient. 



3. It is not necessary to give reasons for regarding the parietal foramen (in relation 

 to the vestige of tlie pineal eye) as a primitive character. It is absent in three species 

 only of the genus Lacerta — L. jacksonii, vanereselli, and echinata — referred to different 

 sections ; also in a few African species of other genera "f". 



4. Considerations derived from the study of other families of Lizards lead me to 

 assume that the original condition of the nostril is to be pierced in the centre of a 

 single nasal shield. This condition is not found in any of the Lacertidtie. The next 

 step is for the nasal to divide into two : nasal proper and postnasal, without the first 

 labial entering the nostril, as we find in some species of Nucras and, as an exceptional 

 occurrence, in Lacerta agilis and Lj. parva. As the nomenclature of the shields round 

 the nostril has given rise to misunderstandings in X. agilis, due to a variability in that 

 species, such as we do not find in any other, it is well to deal here fully with the matter ;J;. 

 As becomes a species which is held to be the starting-point of several diverging scries 

 of forms, Lj. agilis is evidently in a fluctuating state as regards a character which has 

 been deemed of great importance for the definition of species, even' of genera. 



In their key to the identification of the species of Lacerta, Dumeril and Bibron § 

 define L. agilis (stirpium) as having " deux naso-frenales (= postnasals) superposees, 

 la superieure un peu en arriere de I'inferieure," and L. viridis as with " deux naso- 

 frenales superposees bien regulierement," and this diagnosis has been copied by many 

 later authors. If, however, we turn to the description of the species a little further 

 on in the same work, we find a statement which throws doubt on the interpretation of 



* Cf. Leydig, ' Die in Deutscliland lebenden Arten der Saurier,' i)ls. i.-iii. (1S72); Degen, P. Z. S. 1911, 

 1-. 23, "fig. 6. 



t Cf. Degen, i. c. p. 30. I have previously used the presence or absence of the foramen for distinguishing 

 species in the genus Draco (P. Z. S. 1897, p. 198). 



+ The interpretation which I gave of tlie nasal and loreal sliields in the 'Catalogue of Lizards,' iii. p. Ifi, 

 has been followed, and supported by a series of suggestive illustrations, by Mehely, in Zichy's Zool. Ergebu. 

 z. Asiat. Forschungsr. ii. p. 51, pi. vii. (1901). 



§ ' Erpetologie Generate, ' v. p. 189. 



