1888.] THE CARPUS AND TARSUS OF THE ANURA. 145 



SO, the arteria interossea will not help us in the least in estimating 

 the morphological value of the astragalus and calcaneus. 



Wiedersheim asserts (36, p. 211) that in the astragalus we have 

 " ein vereinigtes Tibiale und Intermedium." Gegenbaur (18) and 

 Born, on the other hand, are inclined to regard the tibiale as its sole 

 representative. Proof of the former statement is not forthcoming ; 

 and in spite of the most diligent researching, we have been unable 

 to discover, at any stage, the remotest trace of anything at all com- 

 parable to a third proximal tarsal. Future research may, perhaps, 

 demonstrate its existence ; but, mindful of the elongation of the 

 earliest rudiments of these elements, we incline to the belief that the 

 missing one (? intermedium) has disappeared beyond all recognition, 

 even during the embryonic period. 



c. Tarsalia 4 and 5. — In no Anuran foot hitherto described have 

 there been recognized more than three distal tarsal elements (tarsalia). 

 Examination of the Plates will show that when these remain distinct 

 they are directly associated with the hallux and the two next digits 

 (ex. Plate VII. figs. 8 and 10). The tarsalia of the two outermost 

 digits (4th and 5th) would thus appear to be absent. Gegenbaur 

 first drew attention to the existence, in certain genera, of a ligament 

 (figs. 10, 17, and 19) which passes between the tarsal of the third 

 digit and the head of the fifth metatarsal. He described its relations 

 minutely (18, p. 61), and concluded that " er reprasentirt in ligamen- 

 tosem Zustande Theile, die unter anderen Verhaltnissen als Knorpel 

 gebildet sind." This structure has been recorded in Hyla, Rhino- 

 derma (Gegenbaur), Pelobates (Gegenbaur, 18 ; Bayer, 2), Disco- 

 glossus (Wiedersheim, 36, p. 211), and others, and to the list we are 

 able to add (c/. Part II.). 



Born says of Phryne {Bufo^) vulgaris (3, p. 444) " im Band- 

 polster unter der Basis von Metatarsale IV. traf ich einmal einen 

 deutlichen Rest von Knorpelgewebe, was die Gegenbaur' sche Deut- 

 ung dieses Bandes als Homologon eines Tarsale IV. durchaus 

 bestatigt." We find that in the adult of Alytes ohstetricans this 

 ligament (fig. 10) carries a well-marked nodule of cartilage, which 

 lies between the applied heads of the 4th and 5th metatarsals. 

 That this represents one of the missing tarsals is hardly to be 

 doubted from its relationships, but, from its position, it is difficult 

 to say which. Gegenbaur goes on to assert (p. 61), " wenn man 

 das auf ein blosses Ligament reducirte Tarsusstiick einem der bei den 

 iibrigien Amphibien nachgewiesenen Elementarstiicke vergleichen 

 will, so kann man in ihm nur nach Massgabe der Betheiligung des 

 Metatarsus das Tarsale 4 und 5 erkennen, welches bei den Tritonen 

 schon durch ein einziges Stiick dargestellt war." In Bufo, Sylodes, 

 and Hyla (Plate VIII. fig. 19) the ligament enters into an extensive 

 connection with the head of the fifth metatarsal, like that originally 

 figured by Gegenbaur (18, pi. 4. fig. 13) for the first-named genus. 

 It fuses (fig. 23) with the postaxial articular border of this bone, and 

 the head of the same is seen to be obviously enlarged as the result of its 

 attachment^. It becomes a question of considerable interest, therefore, 



' See Boulenger (7, p. 303). 



- Cf. Xenophnjs, Plate VIII. fig. 17. 



