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Show 1899.] THE CARPUS OF CTENOMYS. 431 to its having been fused (" assimiliert") with the terminal phalange. The condition described in Ctenomys etc., while supporting the first part of Pfitzner's contention, seems however to point out, that in part at least of the Mammalia the disappearance of the second phalange has been brought about by elimination and not by " assimilation." In the pes of the Insectivore Ohrysochloris, the phalanges of all the five toes are reduced to two, and all the five toes show a dorsal ossicle riding on the interphalangeal articulation. This coincidence would seem to be significant; but I have at once to state, that in the manus of Oryzoryctes tetradactylus, which has the normal number of three phalanges in the four digits present, I have found the ossicle in question on the distal interphalangeal articulation of the second digit, and do not doubt that it was present on the others also. The only recorded dorsal ossicles of M a n occur on the metacarpophalangeal articulation of the thumb, and are noticed by Kulmus •; one case also having been found by Pfitzner2; in the same place, on the great toe an ossicle is recorded by Kulmus3. In the Canidae, dorsal ossicles are limited to the metacarpo- and metatarso-pha-langeal articulations \ The dorsal ossicles of the manus of Talpa europcea have been figured repeatedly (Blaiuville, Owen, Flower, &c), but nowhere do I find a reference made to them in the description of the skeleton, which almost seems to show that they have not been recognized as free ossicles, but considered to be processes of the phalanges. In this Insectivore the three middle fingers of the manus have each two dorsal ossicles, one on the metacarpo-phalangeal articulation, and one on the proximal interphalangeal. In the first and fifth digits only the latter articulation shows an ossicle. In the pes I find them only on the proximal interphalangeal articulatious of all five toes. In a skeleton of Condylura, the dorsal ossicles seem to have been partly cut away, so that I cannot make a definite statement. It is noteworthy that, on the proximal interphalangeal articulation of the fifth digit and on the homonymous articulation of the fourth toe, two ossicles are present. In a mounted skeleton of Myogale moschata in the Natural History Museum, I find dorsal ossicles on the proximal interphalangeal articulations of the second, third, fourth, and fifth digits (on the latter there are two ossicles). In the pes, the articulator has almost thoroughly done his " duty," for there is only one dorsal ossicle present, viz., on the proximal interphalangeal articulation of the third toe. In Oryzoryctes tetradactylus, dorsal ossicles, in addition to the above-mentioned, occur also on the second, third, and fourth proximal interphalangeal articulatious of the manus, as well as on the same articulation of the fifth toe, and may have been cleaned away in the other proximal interphalangeal, 1 Kulmus. 'Tabular anatomicse,' p. 62 (1732); id., Miscellanea Med. Phys. ii. p. 328 (1720). Quoted from Pfitzner, Morph. Arb. i. pp. 604, 742 (1892). 2 Morph. Arb. i. pp. 604, 685 (1892). 3 L.c; cf. Pfitzner, I. e. p. 742. 4 See Pfitzner, Morph. Arb. i. p. 603 (1892). |