364 



MKRISTK' VARIATION. 



[PART i. 



bones" were separate . a> -hewn in Fig. 107 C. The fore feet of the 

 --HUH- animal wen- in the cnndition described in (1) b. [See No. 537.] 

 M \K-II. < i. < '.. Am. Jour. ></'., XLIII. 1*92, pp. 340 and 345. 



C. 



Fi'.. luy. Limb bones of a polydactyle horse. 



A. Loft fore foot. No. 537. 



K I.i't't hind foot. No. 535. 



C. Tarsus of right hind foot from the inside. No. 535. 



*;. navicular. ch, cuboid. 4, ecto-cuneiform. 1, 2, 3, three bones placed as 

 cuneiforms. t<l, trapezoid. tin, trapezium. it, iinciform. m, rnagnum. 



I. II, III. IV, numerals affixed to the mctacarpals on the hypothesis that these 

 are tin ir limnologies. Cp. Fig. 10*, which is lettered on a different hypothesis. 



(After MAHSH.) 



b. Fu"i- nu'ttifitrjHils. 



This condition is a higher manifestation of the variation seen 

 in the eases just given. In Xo. 533 the digit II was developed and 

 in addition the trapezium had appeared ; in the cases now to be 



1 MAKSII introduces this case in support of a contention that these variations are 

 "f the nature of lo .< rsion. Upon the same page appears the statement that "in 

 speeimen examined, where the carpal or tarsal series of bones were preserved 

 and open to inspeetion, the extra digits were supported in the usual manner," /. c., 

 p. 345: thi- a--ertion i* hardly in agreement with the previously stated fact that 

 the mi tatarsal II i- -upported by tiro cuneiform bones. On p. 349 Marsh comments 

 "ii the presence of five bones in the di>tal row of the tarsus, and from the expres- 

 -ions iiM'd it is implied that five such bones had been met with in other polydactyle 

 hind feet. A number \ alternative explanations are proposed; (1) that the five 

 tai>al- correspond "'" those of the reptilian foot"; (2) that the lirst may be a 

 amoid " ; >''} that the t;r>t may he a remnant of the first metatarsal, for such 

 a rudiment "apparently exists ill some fo^il hoi>es." With conjectures of this class 

 mnrphi'loji>ts are familiar. Into their several merits it is impossible to inquire, but 

 it may lie mentioned that the real ditliciilty is not the presence of the cuneiform 

 marked 1, but the fact that the tarsal element of the digit II seems to have been 

 double, and that the dibits in reality are not supported in the usual manner. 



