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



between the first tarsal and the astragalus, being in fact absolutely 

 central and in a position which cannot, by any stretch of imagina- 

 tion, be said to be "in einer Eeihe mit den Tarsalknorpeln." It 

 would be more correct to say that the 1st metatarsal, 1st tarsal, and 

 naviculare are here disposed lineally. 



Examination of the Plates will show that the relative size of the 

 naviculare is in no way proportionate to that of the pre-hallux, as 

 might be expected were Born's hypothesis tenable {cf. figs. 3, 10, 12, 

 & 17) ; it is rather the reverse. Choice appears to he between two 

 alternatives : the naviculare has either grown in and displaced the 

 hallux tarsal proximally (as the Discoglossidce would suggest, figs. 

 8 & 10, in which case the condition of the latter would, in this 

 family, be secondary) or it has undergone a reduction proportionate 

 with an increase in size of the same. Recent observers are agreed 

 as to the lowly position of the Discoglossidce \ and it therefore 

 becomes a question of first importance as to how far the arrangement 

 just described in them is primary. 



In the youngest Discoglossidce examined by us {cf. p. 104), no 

 appreciable difference could be detected in the relative proportions 

 of the two elements under consideration as compared with the adult ; 

 we have here, then, strong reason for regarding the condition exempli- 

 fied in them as really primary. The matter, however, presses still 

 more closely. Examination of those forms in which the pre-hallux 

 is regularly segmented (fig. 19), shows that that segment which 

 Born regards as its metatarsal {ph. i.) is generally disposed in a 

 line with the naviculare, re' {cf. figs. 13 & 19). In Pelodytes, how- 

 ever (fig. 13), and less conspicuously in Alytes (fig. 10) and Hyla, 

 the first-named element is intimately connected with the adjacent 

 hallux-tarsal (1) by means of a well-defined ligament, which runs 

 distally to the naviculare. Comparison of this ligament with that 

 previously referred to as the representative of the 4th and 5th 

 tarsalia, leaves little room for doubting, if argument from analogy 

 is worth anything, that Born's metatarsal of the pre-hallux is, in 

 reality, its tarsal. If this be admitted, there can no longer be any 

 doubt of the homology of Ecker's naviculare (?«') with the os centrale 

 tarsi. 



This determination brings the tarsus of the Anura into closer 

 harmony with that of the other and, especially, the higher Vertebrata 

 than is now generally admitted, while it sets at rest further doubt as 

 to the value of the hallux-tarsal. 



Finally, Ecker has shown (17, p. 128) that the tendon of the 

 adductor longus digiti primi muscle {m.a.l. of woodcut, fig. C, p. 1 76) 

 is inserted into the naviculare. We have found this to be invari- 

 ably the case whether the hallux-tarsal is present or absent. It 

 follows, therefore, that all possible source of confusion between that 

 element and the naviculare is at an end. 



g. Pre-hallux {Calcar). — The skeleton of the pre-hallux was first 

 figured by Rosenhof (32) ; he described it {Pelobates, p. 84) in the 

 words " tandem etiam in sceleto hoc notari meretur singularis quidam 

 1 Cf. Cope (12, p. 104) and Boulenger (7, p. 444). 



