SIWALIK AND NARBADA CHELONIA. 
3—157 
indications that tlie recent gigantic tortoises of the far distant islands of the Indian 
Ocean are sprung from an allied branch. The inference may thus be drawn that 
while many of the smaller forms have clung to the continent of Asia with but a 
comparatively slight amount of change from the Siwalik epoch to the present day, 
the larger ones have entirely succumbed in the contest with the higher mammals of 
the continent, and are now only represented by distant cousins in regions entirely 
free from such forms of life, or by much smaller species on the Asiatic continent. 
The comparatively small number of forms described in the following pages 
when taken in connection with the large number belonging to particular groups 
indicates that we are at present only acquainted with a small moiety of the whole 
Siwalik chelonian fauna ; and from the extremely interesting nature of the species 
that are known to us the attention of collectors may be particularly directed to the 
acquisition of additional speciu'ens. 
Finally, it may be observed that the intimate affinity exhibited by the majority 
of the Siwalik tortoises with those now inhabiting India affords one of the strongest 
arguments for the late geological age of those deposits. 
Family I. : TESTUDINID^. 
Shell convex, covered with horny plates ; feet c]ub-shaped and adapted for 
walking (hind-feet partially webbed in Manouria) ; pygal plates usually united, but 
separate in some recent and extinct Oriental forms. Plastron (in recent forms) 
concave in males, flat in females. 
Genus I. : COLOSSOCHFLYS, Falconer and Cautley.^ 
Shell as in Testudo,^ but with the pygal plates not united, and the plastron produced 
anteriorly into a pair of cornua, supported on the ventral aspect by a strong 
triangular keel on winch the gular plates are borne. Pectoral plates unknown. 
The genus is exclusively Indian, and now extinct. 
Species : Colossochelys atlas. Falconer and Cautley.® 
Syn. Megalochelys sivalensis, Falconer and Cautley.^ 
(Twice the size of Testudo elephantma.) 
History. — This species was originally named Megalochelys sivalensis, but the 
designation was subsequently changed to Colossochelys atlas ; the term Colossochelys 
being employed as a subgenus of Testudo. As subgeneric terms are objectionable, 
and as the present species differs from Testudo by the non-union of the pygal plates, 
and from Manouria by the form of the epiplastron, the term Colossochelys is retained 
1 ‘ Proc. Zool. Sbc.’ 1844. p. 54. (As a subgenus.) 
2 The definition of Te/tiudo may he given as follows, viz .\ — Shell usually solid, entirely hony and immovable, but 
sometimes of extreme tenuity ; pygals united ; gulars usually double, but sometimes (Mascarene tortoises) imited ; nuchal 
plate present or absent. 
3 Loc. cil. 
4 ‘ Journ. As. Soc. Beng.’ vol. VI. p. 358. (1837). 
