OlfJ THE EPISTEERAL APPARATUS OF MAMMALS. 



553 



velopment as those of Miiridae. In Orocidura (Jeucodon) each cla- 

 vicle terminates in a peculiar rounded and ossified epiphysis, which 

 is separated from the shaft of the bone by a thin layer of cartilage, and 

 is joined by a conical elongated cartilaginous piece, which is firmly 

 attached by connective tissue to the anterior border of the manubrium 

 sterni, near the median line. In the interior of the cartilage I have 

 found an osseous nucleus : I have not been able to determine the 

 presence of an intervening joint, either here or in Sorex (Sorex ara- 

 neus) where the episternals (Fig. 5) are still shorter than in other 

 species, and, at least in the single specimen I examined, presented no 

 ossification. 



Fig. 5. 



St \ 



Episteraal apparatus of SonxpygmcEus { Shrew) : — ep, episternum ; e, clavicle ; 

 c', first rib ; st, sternum. 



In Arctomys (Arctomi/s Ludoviciana) a short episternal exists 

 on each side, externally cartilaginous, but containing a true bony 

 nucleus in its interior, which, in my specimen, is perfectly distinct, 

 even in the dry condition. There appears, however, to be a change 

 here from the condition which has been already described as existing 

 in the Eodentia and Insectivora, in that the episternum is applied, not 

 to the posterior surface, but to the lateral and upper edge of the very 

 broad manubrium sterni, a feature, however, that requires a closer 

 investigation in moist specimens. These forms are associated with 

 those met with in certain representatives of Hodentia and Insectivora 

 as in the Hamster and Hedgehog, both of which in opposition to the 

 above-mentioned animals, have Avell-marked clavicles, but only feebly 

 developed episternals. As regards Cricetus the expanded extremity 

 of the clavicle is connected with a cartilaginous piece of about three 

 N.H.R.— 1865. 2 P 



