224 MR. A. H. GARROD ON TOLYPEUTES TRICINCTUS. [Feb. 19, 



so well described its structure. Dr. Murie's figure, being based upon 

 a photograph of the specimen, is thoroughly reliable. 



M. Is. Geoffrey St.-Hilaire has so well differentiated T. tricinctus 

 and T. conurus that it will be necessary for me only to mention that 

 iu the former there are five toes on the fore feet (as in the Society's 

 specimen in my possession), whilst in T. conurus, following the 

 account of the discoverer of the species, there are " trois doigts seu- 

 lement, avec le rudiment d'un quatrieme, aux pattes anterieures (ce 

 rudiment represente le doigt interne). Point de doigt externe." 

 The same remarks apply to T. muriei ; for in the specimen iu the 

 British Museum there are four toes on each fore foot, whilst in Dr. 

 Murie's example the pollex was not present. 



The tail, with its infundibuliform armature, is distally covered 

 with four pairs of small rows of plates, arranged in longitudinal lines, 

 there being one superior and one inferior pair, one supero-lateral and 

 one infero-lateral. In T. tricinctus the whole organ is flattened from 

 above downwards ; in T. conurus and T. muriei it is not so. Two 

 and a quarter inches appear to be its extreme length along its dorsal 

 curve in all but the largest individuals, where it may reach two and 

 a half inches. I do not find that the different species differ in the 

 length of this appendage, which is correlated, as far as its length 

 goes, with the length of the head, on the right side of which it 

 always lies when the animal is rolled up 1 . 



I can find no important differences among the species in the ante- 

 rior portion of the carapace. In the three free transverse semizones 

 T. conurus and T. muriei agree, and differ from T. tricinctus in that 

 the terminal or marginal lateral scutes of each zone (which with the 

 scute above on each side of each zone are less tuberculated than the 

 rest, to reduce the friction when the animal rolls itself up) are more 

 detached from the second scute, are more rounded, and are smaller 

 proportionately. 



In the posterior moiety of the carapace of T. conurus and T. mu- 

 riei fifteen, sixteen, seventeen, or eighteen rows of scutes can be 

 counted along the middle line from before backwards if the marginal 

 scutes are included in the numeration ; in T. tricinctus I never find 

 more than thirteen or fourteen rows. 



In T. tricinctus only there is a triangular area composed of small 

 scutes, with its apex directed downwards, and basally in coutact 

 with the cephalic shield, which interpolates itself between the eye 

 and ear on each side. 



The following measurements of the specimens of the different 

 species in the national collection may prove of service in determining 

 the proportions of each. They demonstrate that the head is decidedly 

 shorter than the anterior moiety of the carapace in T. tricinctus, 

 whilst in T. conurus and T. muriei it is nearly always longer ; that 

 in T. tricinctus the head is more than half the length of the poste- 

 rior moiety of the carapace, whilst in the two other species it is not 

 so much as half that measurement. 



1 Dr. Murie figures the tail on the left of the head (I. c.) — the photograph 

 from which the drawing was made not having been reversed, most probably. 



