432 DR. 1. 1. roRSTTH MAJOR ON [Apr. 18, 



as well as in the metacarpo- and metatarso-phalangeal articu- 

 lations. 



Among the Rodents, I have for the present come upon dorsal 

 ossicles — apart from the one on the first dis;it — in LfKjomys, viz., 

 on the metacarpo-phalangeal articulation of the second, third, and 

 fourth digits, and in Spahix. In the manus of the latter, dorsal 

 ossicles are present on the proximal interphalangeal articulations of 

 the 2nd-5th fingers ; in the pes, on the interphalangeal articulation 

 of the first, and on the proximal interphalangeal articulations of 

 the four other toes. As regards Edentates, it has been stated that 

 " a sesamoid bone is developed on the dorsal side of the metacarpal- 

 phalangeal articulations" of Oryctcropus^. In the skeletons of the 

 Cape Anteater available to me, all traces of these had been care- 

 fully made to disappear. 



From the above fragmentary evidence it can be argued that 

 careful research will show these dorsal " sesamoids " to be a not 

 uncommon occurrence ; it will then be time to investigate them 

 more closely. They too may ha\e been originally intercalated 

 between the phalanges, and would point towards a more remote 

 condition than does the interphalangeal dorsal ossicle of the thumb. 

 As to the opinion that their function is to facilitate the sliding of 

 the tendons over osseous protuberances, and to enlarge the angle of 

 insertion of the tendons, I may be allowed to refer to what Pfitzaer 

 has said on the subject ^. 



n. 



The pisiform of Ctenomys is composed of two bones (figs. 1 & 2), 

 as found by von Bardeleben in Bathyenjus maritimiis \ and more- 

 over the distal one has, in one species (fig. 2), a horny sheath, 

 comparable to the nail-like structure — found by O. Thomas and 

 described by von Bardeleben* — on the so-called prsepollex of 

 Pedetes ; and to a somewhat similar one stated by Prof. Howes 

 to overlie the eulai'ged "prsehallux" of Cercolabes'. The two dis- 

 coveries of von Bardeleben" — by the way, the two bones of 

 Pedetes were described by Meckel in 1825 — are among his chief 

 arguments in support of his assumption of a sixth and seventh 

 finger ; accordingly, the proximal bone of the pisiform of Ba- 

 thyergus was considered "as in all probability the carpal, and 



^ Flower : ' An Introduction to tbe Osteology of the Mammalia,' 3rd ed., 

 p. 309 (1885). 



^ " Erlautern wir dies an dem Beispiel der Sesaraa dorsalia. Wenn irgend 

 Jemand, so batten alsdann die ' Greii'hiinder ' solche nothig, die Affeu iind der 

 Mensch ; warum flnden wir sie aber statt dessen bei den Caniden, bei denen das 

 betreffende Gelenk fast immer in Ueberstreckung bleibt ? VVaruin nieht eher 

 bei den Feliden, die in diesem Gelenk schon viel energischer beugen ?" (Morph. 

 Arb. i. p. 610, 1892). — Besides, the.se dorsal ossicles of Canid;B are only loosely 

 connected with the extensor tendons ("iin die Strecksebnen nur locker ange- 

 heftet") (id. ib p. 604) See also ib. pp. 567-571, 609-612. 



3 P. Z. S. 1889, p. 260, pi. XXX. fig. 3. 



^ Id. ib. 



° L. c; Bardeleben, I. c. p. 260, footnote. 



^ K. T. Bardeleben : '' Hand und Fuss. Referat erstattet auf der 8. Vers. d. 

 Anat. Ges. in Strassburg'' (Verb. d. Anat. Ges. viii. p. 283, 1894). 



