172 PROF. G. B. HOWES AND W. RIDEWOOD ON [Mar. 6, 



In Cheiroleptes the proximal segment is by far the stronger ; 

 while in Heleioporus the second one is robust and forcibly reminds 

 one of the calcar in Pelobates. 



f. Engystomatid^. 

 Examined : — 



Rhinoderma darwini, 



Phryniscus Icevis, varians, and cruciger, several. 



Brachycephalus ephippium. 



Callula picta ; C. baleata. 



Microhyla, ? sp., 2. 



Rhombophryne testudo. 



Fore Foot (figs. 30, 32). 



The carpus in this family stands boldly out from that of all other 

 Anura, with respect to the extraordinary tendency towards fusion 

 of more or fewer of its elements with each other or the adjacent 

 metacarpals. 



The naviculare shows a tendency to hecome proximal in all; in 

 Phryniscus (fig. 30) its ascending spur is strongly marked, nearly 

 meeting the radius'. This bone is implicated in the simplest 

 fusion observed {Microhyla), becoming confluent with the lunatum. 

 If our determinations of the morphological value of the carpal 

 elements are sound, it follows that in this almost unparalleled feature 

 we have the precise converse of the unique phenomenon encountered 

 in Pipa (p. 1(32) — there, our postaxial ceiitrale is in confluence with 

 the proximal postaxial element ; here, the preaxial one enters into 

 similar relationship with the proximal preaxial bone. 



Brachycephalus ^ stands alone, among all forms examined by us, in 

 that carpale 2 early unites with its corresponding metacarpal. 



The above simple cases fade into insignificance beside that of 

 Rhombophryne " (fig. 32). Here, all four carpalia and our two 

 centralia have become welded into one great mass, interposed, as it 

 were, between the lunatum and ulnare and the heads of the meta- 

 carpals. The boundary lines of its originally distinct constituents 

 may be, for the most part, followed. 



Remarkable indeed is the condition met with in Phryniscus, for 

 here the variations are not even generically constant. In the two 

 specimens of P. Icevis examined, all the parts were free (fig. 30), 

 while in P. varians carpale 2 had fused with the naviculare. In P. 

 cruciger vie ioxxwdi a unique state of affairs, carpals 1 & 2, metacarpals 

 1 & 2, and the naviculare all being firmly anchylosed together. It 

 will be observed that here, as in Microhyla and less conspicuously 

 in Brachycephalus, the whole tendency is towards imparting rigidity 

 to the preaxial limb-border ; it is not surprising, therefore, to find the 

 naviculare sending up a radial spur, and, in doing this, appearing to 

 become proximal. 



^ As already pointed out by Gegenbaur (18, p. 17). 

 ' One specimen only examined. 



2 



