1899.] THE CARPUS OF CXENOMYS. 433 



the distal as the metacarpal segment of the postmiuimus." ^ In 

 his last utterances on the subject', neither the pisiform and cal- 

 caneus, nor the so-called prsepollex and prsehallux, are considered 

 as true carpal and tarsal bones, but " they have the same rank and 

 position as the metacarpal and metatarsal bones." 



AVhat for palaeontologists has been scarcely doubtful from the 

 beginning of the discussion, becomes still clearer by the recent 

 researches, viz., that the Tetrapoda have always been peuta- 

 dactyle ^ ; so that we may use " Pentadactylia " as synonymous 

 with Tetrapoda. The remains of supernumerary rays must be 

 traced to stages beyond the tetrapodous. Although a linger (toe) 

 is a ray or part of one, the more general term " ray " (Strahl) is not 

 synonymous with hnger (toe) ; to use the two terms promiscuously 

 is e(.|uivalent to delibei'ately confusing the discussion. 



Where we meet among Mammals with an especial development 

 of those supernumerary rays, this condition can always be traced 

 to their secondary adaptation to special f uuctions, as was long ago 

 insisted upon by Wiuge and others *. 



As to the pisiform, a more or less ossified distal element seems 

 to be a common occurrence among Eodentia; apart from Bathy- 

 erc/us and Otenomi/s, I find it in all the species of Mas up to the 

 present examined (ijcl. fig. 4), including Mus decamanus and Mus 

 alexandrinus ; it is present too in Brachyuromys i-amiroliitra and 

 in Arvicanthis niloticus (fig. 5, 2^d-)- In all of these its special 

 development is apparently due to an adaptaliou to either climbing 

 or fossorial functions (to the latter in Bathyergus, Ctenomys, Mus 

 nativitatis), or to both combined. 



The so-called os Daubeutonii of the Gibbon, about which more 

 will be said farther on, is according to an observation by Leboucq, 

 the most proximal part of the Mammalian pisiform ; from its 

 position it cannot be considered as an " ulnare antebrachii " (Thile- 

 nius) ; but seems to be the only part of the pisiform belonging to 

 the carpus. 



1 P. Z. S. 1889, p. 260. 



" P. Z. S. 1894, p. 373.-' Hand und Puss,' p. 312. 



^ C'f. e. g. Emery, in Semon's ' Forschuugsreise,' ii. p. 399 (1897) : " Die Zahl 

 der ecbten Finger und Zehen ist und war imruer auf t'iinf beschrankt." 



^ In his " Reterat" (p. 336), vou Bardeleben admits tliat this may be the case 

 with the "proepollex" of Pedctes, although on a preceding page the same had 

 been adduced as a convincing argument in favour of his case : "... dritteiia 

 suchte Eef. nach Saugetiereu, die uioht nur das Eucliment eines Prsspollex, 

 sondern einen ' wirklichen Finger ' hiitten — im Sinne Gegenhwur's, der dafur 

 ein Metacarpale und einigc Phalangen verlangt. 



" Nacb dem alten, so recbt fiir den Wahlspruch eines Naturforschers geeigneten 

 Worte : ' Suchet, so werdet ihr finden,' gelang es damals (1889) auch, nicbt 

 iiur bei Beptiliun, fossilen und lebenden Schildkroten u. a. einen Prtepollex und 

 Prashallux nachzuweisen, sondern sogar Saw^ei!/ere zu finden, bei denen der Prse- 

 pollex {Fedetes capensDi), oder der Postminimus {Bathyergus maritimus) aus 

 2we« Knocbenbesteht . . . .Pedeies besitzt aber nicbt nur zwei Knochen im Pra;- 

 poUex-skelet, sondern einen wirklichen 'Finger' mit einem breiten, fein- 

 gestreiften Nagel, mit Falz etc., wie Eef. fiir die drei Londoner Exemplars 

 festgestelh hat! " {I. c. p. 283). 



