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



esculenta the arteria brachialis sends up a branch, which perfo- 

 rates the carpus ventro-dorsally, for distribution to the integument 

 and parts adjacent. In some forms (ex. Biscoglossus, figs. 5, 6,f.i.) 

 the bones of tlie proximal row become definitely notched at this 

 point, enclosing that which we would term ' a foramen intercarpi 

 for passage of the artery. Born has demonstrated the same fact for 

 certain Lacertilia (4, pp. 2-3); while Wiedershiem % Baur (1, 

 pi. i. fig. 4), and others have done so, less conspicuously, for the 

 Urodela. Examination of the several descriptions and figures shows 

 that the perforation invariably takes place between the postaxial 

 (ulnare) and central (intermedium) elements of the proximal series. 



In certain Urodeles a confluence takes place between these 

 skeletal units ; and when this is the case the ulnare and intermedium 

 are invariably those which fuse, and in some of these cases the 

 artery in question perforates the confluent mass. Taking this 

 fact into consideration it is clear that the ulnare is the only element 

 which, under all circumstances, can lie postaxially to the blood- 

 vessel. Seeing, moreover, that the artery agrees in all investigated 

 cases in every known detail of distribution, it is obvious that, in 

 it, we have a convenient landmark by which to estimate the mor- 

 phological value of the proximal carpals. This said, further argu- 

 ments are unnecessary in order to show that the so called " pyramidale " 

 of Duges and Ecker is the ulnare, as Gegenbaur showed and as all 

 subsequent writers admit. 



e. Lunatum (/.) — The extraordinary position in which the fore 

 foot of many living Anura is carried has resulted in a rotation 

 of the parts of the same upon the coalesced radius and ulna, of such 

 a nature that the distal extremity of the ulna comes to be directed 

 towards the palmar surface of the fore foot itself. This rotation is 

 most marked in Dactylethra, Hyla, Pelobates, Pseudis, and Rana ; 

 and it is instructive to find that the tadpoles of these genera do not 

 exhibit it. The distortion resulting from it is such, that we often 

 found it impossible (ex. Pelobates, fig. 18) to obtain a comprehensive 

 view of the carpus without first disarticulating the radius. The 

 importance of this observation is by no means slight, for there can 

 be little doubt but that we are to seek the clue to the remarkable 

 delineations of some authors, to displacement of these parts, conse- 

 quent upon their having flattened them out. 



From what we have said (supra) concerning the course of the 

 arteria brachialis, it will be clear that the lunatum can only represent 

 the radiale or the intermedium — one or both — of the less modified 

 forms. Gregeubaur was unable to make up his mind (18, p. 13) as 

 to whether this bone represents a confluence of these two elements 

 or a persistent radiale — the intermedium having disappeared. He 

 further suggested the possibility that the last-named may have been 

 absorbed by the radius and ulna during coalescence. 



Born puts forward, in his latest communication (6, p. 62), the 

 startling supposition that the lunatum is the intermedium. He bases 



1 Uniformly with the /. intertarsi of the hind foot (p. 144). 

 » Morph. Jahrb. vol. 2. (1876). 



