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Show 1888.] THE CARPUS AND TARSUS OF THE ANURA. 165 According to Born (6, p. 62) the rudimentary pollex may, in Bombinator, either bear two phalanges or be wholly absent. In all our specimens we find that it bears two segments (po. ii. & iii.), irrespective of its carpal (po. i.). In Discoglossus and Alytes there is but one segment other than the carpal present; in the male Discoglossus this becomes fully ossified and expanded. During ossification of the leading elements in Discoglossus, a central deposit takes place in each (I. n. fig. 5 ) ; soon, however, a differentiation of the ossific centre into a superficial spongy annulus and a central denser core takes place (pk, fig. 5), leading up to the curious condition of the adult bones (fig. 6) already noted (p. 143). Hind Foot (figs. 8 & 10). Gegenbaur was in error in asserting (18, p. 60) that in Bombinator the separation between the astragalus and calcaneus is complete. In even the youngest larva examined by us these two elements had already become confluent, bearing a common expanded epiphysial cartilage. Born claims for the same genus (6) a range of individual variations in the tarsalia far exceeding anything which we have observed. In all our specimens the tarsalia of digits 1, 2, & 3 are distinct, that of the third being invariably the largest. Tarsalia 4 & 5 are represented by a ligament, which in Alytes alone carries a nodule of hyaline cartilage (p. 145). The naviculare (centrale, n') is, in all, large, and so placed as to separate the hallux-tarsal (1) from the astragalus, the epiphysial end of which is excavated so receive it. This element is always the first to ossify, the calcar follows, tarsalia 1, 2, 3 remaining for a considerable time unossified. The calcar never consists of more than two segments, and is in all small. Born, in opposition to Leydig, regards the solitary piece present in Alytes (fig. 10, ph. i.) as the metatarsal (our tarsal) + the phalanx of the sixth toe. W e have been unable to detect the presence, at any stage, of a second segment ; we hold, therefore, that the element in question is really the hallux-tarsal. b. PELOBATIDCE. Examined:- Xenophrys monticola: 3 specimens measuring respectively 70, 40, and 26 m m. Pelodytes punctatus : 3 adults and a tadpole. Pelobates fuscus : an adult <$ and one very young specimen. Fore Foot (figs. 11, 14, 15, 16, 18). That which most characterizes the carpus in this family is the relatively large size of the four carpalia (cf. p. 158). The 5th carpal is represented in a ligament, the detailed relationships of which have been already described (p. 154). This, as will be seen in fig. 15, becomes suddenly constricted at its point of insertion into |
