1888.] THE CARPUS AND TARSUS OF THE ANUUA. 147 



further, that the connection between the innermost tarsal (1) and 

 the head of the second digit is purely secondary, and that the first- 

 named is really the tarsal of the hallux, displaced, as it were, in 

 sjmpatliy with its dwarfed neighbour. 



Ecker speaks (17, p. 61) of the cuboideum in Bufo as consisting 

 of two pieces. We find that in that genus, as in Leptodactylus, a 

 similar shortening up of this bone takes place (c/". fig. 23) ; there 

 can be little doubt therefore that Ecker was misled by that, pre- 

 cisely in the manner indicated above. 



The cuboideum, then, must be held to represent the confluent 

 tarsalia 2 and 3. We have to record its presence in the Ranidce, 

 Dendrobatidce, Encjystomatidce, Cystignathidce, Bufonidce, Fhjlidce, 

 Dactylethridce, and Pipa. 



e. Tarsale 1 (Hallux tarsal) (i). — This element is of very constant 

 occurrence. Its relations in the Discoc/lossidce are exceptional and, 

 as will be shown below (figs. 8 & 10), interesting; it lies in them 

 under cover of the naviculare (?i'), interposed between it and the 1st 

 metatarsal. Gegenbaur appears, in dealing with Bomhinator, to 

 have mistaken the naviculare for the first tarsal (18, pi. 6. fig. 1 1) ; 

 but this is not to be wondered at, in consideration of the small size 

 of the latter. It is wanting as a distinct element in old specimens 

 of Naiiiwphrys and Phryniscus, and we have found that it fuses in 

 both genera with the naviculare. Born has described and figured 

 it accurately in Rana esculenta. Concerning R. tewporaria he says 

 (3, p. 441) that it " immer in Laufe der Ontogenese bis auf uner- 

 hebliche Spuren schwindet." Strictly speaking, this is not the case, 

 for we are in possession of old examples in which it had persisted 

 as a distinct element (woodcut, p. 1/6, fig. C, I). We are inclined 

 moreover to believe that instead of undergoing suppression, as Born 

 imagines, it more probably fuses with the naviculare as in the two 

 above-named genera. 



f. Naviculare and Fre-hallux tarsal. — Ecker regarded the navi- 

 culare of these animals as analogous (17, p. 61) with the element so 

 named (centrale) in the tarsi of the higher animals. Gegeubaur, on 

 the other hand, who, as before stated, confused it with the hallux- 

 tarsal, sums up his conclusions in the words (18, p. 67), " ein 

 Centrale fehlt." Born adopts this view ; but he differs from 

 Gegenbaur in that he regards the naviculare as the basal segment 

 (tarsale) of the pre-hallux. He w rites (3, p. 448), " von diesen 

 [segments of the pre-hallux] liegt der erste in einer Reihe mit 

 den Tarsalknorpelu, welche Metatarsustriiger sind, ahmt dieselben in 

 Form und Structur nach und ist von den Autoren auch, wie 

 erwiihnt, immerals 'typischer' Tarsalknorpel aufgefasst worden." 

 Bom's determination has been adopted by all subsequent writers. 

 It will thus be seen that the two views entertained as to the mor- 

 phological value of the naviculare are diametrically opposed, and 

 that a settlement of their differences is indispensable to the full 

 determination of the value of the distal preaxial elements. We 

 have already drawn attention to the fact that the naviculare of the 

 Discofflossidee (ex. Bomhinator, fig. 8, Alytes, fig. 10) is wedged in 



