1901.] AFFINITIES OF UDENODON. 170 



The centrale, as seen in the specimen, would appear to be a 

 small element fitted in between the tibiale, the fibulare, and the 

 third tarsale, but it seems probable that the dorsal view of the 

 tarsus would show it to be a much larger element. This is rendered 

 highly probable by the fact that there appears to be an unoccupied 

 gap between the first tarsale and the tibiale. This must either 

 have been occupied by the centrale or the 1st tarsale must have 

 articulated with the tibiale, and in the specimen has been displaced. 

 The positions occupied by the other tarsal elements lead me to 

 favour the former alternative. 



The 1st tarsale (ts. 1, Plate XVII. fig. 5) is a large element much 

 resembling a metatarsal in shape. Its proximal end is expanded, 

 and, assuming that it is in an undisturbed position in the specimen, 

 the outer side of this end articulates with the 2nd tarsale. The 

 proximal end must either articulate with the tibiale direct, or a 

 portion of the centrale was interposed. 



The 2nd tarsale is a very small element, articulating laterally 

 with the 1st and 3rd tarsalia, and most probably with the centrale 

 proximally. It gives support to the 2nd digit. 



The 3rd tarsale is about twice as large as the 2nd. It articu- 

 lates with the 2nd and 4th tarsalia and with the centrale, and 

 gives support to the 3rd toe. 



The 4th and 5th tarsalia (ts. 4, 5) are so closely united that 

 there is some doubt as to whether the element present may not be 

 entirely the 4th tarsale. The element is a somewhat oval-shaped 

 bone with the distal side slightly concave. It fits in between the 

 fibulare and the 3rd tarsale, and possibly articulates with the 

 centrale. It gives support to the 3rd, 4th, and 5th metatarsals. 

 Near its outer end there is an indication of a transverse suture. 

 which seems to point to there being a small 5th tarsale closely 

 united to, if not anchylosed with, the 4th. In dealing, however, 

 with so small a structure, where the, bones so closely resemble the 

 matrix in colour that it is difficult at times to decide what is bone 

 and what matrix, one cannot place much reliance on an indication 

 so minute. 



The hallux has a short quadrangular metatarsal (mt. 1) and a 

 phalanx (ph.) almost exactly similar in shape and size, and a short 

 ungual phalanx less than twice the length of the 1st phalanx. 



The 2nd, 3rd, 4th, and 5th toes are so similar in all respects 

 that a description of any one would suit, with very slight modifica- 

 tions, any of the others. In all four the metatarsals are elongated 

 bones with rounded proximal ends, flattened distal ends, and with 

 their shafts constricted in the middle. The Bret phalanx in all 

 four fcoes is a quadrangular bone slightlj longer than broad. In 

 the fourth toe the phalanx is somewhat stouter than in the others. 

 The second phalanx is a little shorter than the first, and very 

 similar in all Four toes. The ungual or terminal phalanx has in 

 all five toes been provided with a short claw, only Blightl] curved. 



Though the Eore and bind limbs are fairly equal in length, the 

 pes is irery much smaller than the manus. All the digits are much 



12* 



