640 PROF. H. G. SEELEY ON [Aug. I9OO, 



(c) The Tarsus. 



The tarsus is characterized by a great compressed triangular tarsal 

 bone, which consists of two elements blended together. It is com- 

 pressed from back to front ; and I regard the larger part, which articu- 

 lates with the tibia, as the astragalus. It is possible that both tibia 

 and fibula articulate with the same proximal surface, so that the 

 os calcis may project outward as a thick compressed ossification 

 standing beyond the tibia and fibula. There is a proximal surface 

 transversely truncated, the inner half of which, formed by the 

 astragalus, may alone have given attachment to the fibula. 



There is no trace of any bone of the distal row of the tarsus ; 

 and presumably the distal elements of the tarsus were cartila- 

 ginous. 



The great transverse width of the proximal bone is sufficient to 

 have given attachment to about four digits, but the fifth may 

 have been directed internally, though there is no evidence of this 

 position. 



(d) The Metatarsus and Digits. 



The metatarsals increase in length from the first to the fourth 

 and fifth, but they become successively narrower; the first and 

 second are both broader, stouter bones than the fourth and fifth, 

 and the third is intermediate. They are flattened above, have 

 concave sides, and are somewhat concave on the under side. Their 

 proximal articular surfaces are truncated, with elevated borders ; 

 and the distal ends show a moderate rounding, as of a pulley-shaped 

 articulation . 



The first digit is strong and short, and consists of a single phalange 

 with the sides deeply notched, followed by a claw-phalange in 

 which a strong triangular callosity is developed below the articu- 

 lation. 



The second digit is much longer, and contains three phalanges ; 

 the difference in length being due mainly to the intercalation of an 

 additional phalange. The third digit also includes three phalanges ; 

 the bones are not quite so wide as in the second digit. Their 

 aggregate length is the same. 



In the fourth digit, which is only seen in the superior aspect, 

 there are four phalanges, which are individually rather smaller than 

 in the third digit, and have similarly short proportions, terminating 

 in a sharp claw-phalange, which is convex on the upper surface. 



Of the fifth digit no phalange is preserved. The form of the 

 long metatarsal is consistent with the phalanges having been as 

 well developed as in the other digits. In general form this hind- 

 foot closely resembles the fore-foot of the South African Eury carpus. 

 In the character of the phalanges there is some resemblance to 

 Echidna, but the metatarsal bones are different in being stouter 

 than in the Monotreme. 



