410 
G. J. DE FEJERVARY 
of Depéret’s «loi d’augmentation de taille dans les rameaux phylétiques a) 1 
Whether this rule can be generali.zed with regard to all middle- 
Tertiary forms of F aranus, must be considered to-day as an open question, 
as the very restricted material of fossils at our disposition does not allow 
sufficient study in the matter. As far as the genus Varanus is concerned, 
Varanus marathonensis and Varanus sivalensis most certainly show an aug¬ 
mentation in size.These two partially synchronical forms agree with eachother 
in the increase of size, but differ much in the manner in which they 
set forth the massiveness of their vertebral arches ; whilst F. sivalensis 
preserved the normal dia me ter of its nerve-canal, the 
increase of the thickness of the neural arch was attained in F. marathonensis 
by a contraction of the neural canal. This is a fact worth 
noting with regard to its value in the consideration of bionomie phe¬ 
nomena. This case may also serve as a proof that even when generalization 
is admitted to a certain degree, the mode in which different, 
even nearly related, organisms produce the same — or almost similar — 
tffects, may be of very aberrant nature, thus at each occasion, before judging, 
the special biological circumstances of the r e s p e c- 
eive organism ought to be taken into account as the imme¬ 
diate source of the bionomie factors, the action and the 
result of which we are searching for. 
Hab.: Siwalik Hills, India. 
5. Varanus cf. ? bengalensis Daud. foss. 2 - Pleistocene. 
Varanus dracaena Shaw, Lydekker, Fauna of the Karnul Caves, Mem. Geol. 
Surv, Ind,, Palæont. Ind., Ser. X, Vol. IV, Calcutta, 1886, p. 54, Fig. 10 A — C. 
Varanus dracoena, Nopcsa, B?itr. z. Kenntn. foss. Eid., Beitr. z. Paläont. u. Geol. 
Öst.-Ung., Bd. XXI, Wien u. Leipzig, 1908, p. 47. 
Varanus bengalensis Daud., Lydekker, Catal. Foss. Rept. and Ampli. Brit. Mus., 
Part I, London, 1888, p. 282, Fig. 64A — C. 
Remains of a smaller Varanus- form from the Karnul Gaves were 
referred to this species by Lydekker. They consist, according to the state¬ 
ment contained in his «Fauna of the Karnul Caves» and «Catal. Foss. Kept, 
and Amph.» «mainly of upper and lower jaws and vertebrae» 3 as well as 
of «imperfect limb-bones, probably belonging to this species.» 4 The vertebrae, 
1 Les transform, du Monde Animal, Bibi, de Phil. Sci., Paris, 1907, p. 199. 
a Synonymy concerning the recent V. bengalensis Daud. was omitted 
at this place. 
3 Fauna Karnul Caves, p. 54. 
4 Catal. p. 282. 
