150 



SPECIMENS OF SIRENIA. 



2nd and 3rd metacarpals it shows evidence on the 

 surface of fusion of two originally separate bones. 

 The pollex consists of Mj and no phalanx ; Mji had 

 two phalanges, Mjij three phalanges, Mj^ three pha- 

 langes, M^ , minimus, two phalanges. 



In the adult skeleton, No. 1, the scapula is 12 1 inches 

 in long diameter, 5^ inches in glenoido- vertebral ; the 

 coracoid projects 1^ inch, the acromion Ih inch from 

 the spine. The humerus is 7| inches long, radius 5^ 

 inches, ulna 7 inches, epiphyses all fused ; the carpus 

 has the same number and arrangement of bones as 

 the above specimen ; the metacarpals and phalanges 

 also correspond, except that the pollex has a minute 

 phalanx and the index has three phalanges. 



The skeleton No. 2 closely resembles No. 8, but 

 the cai'pal radiale has been lost. 



9. Tympano-periotic bones, right, of the Dugong, No. 4 in 

 Catalogue. The tympanic is an imperfect ring, the 

 broad end of which is directed downwards, forwards, 

 and inwards, and is swollen on its posterior surface. 

 The two cornua of the ring are fused with the periotic, 

 and the longest diameter is 1^*„ inch ; in form the 

 tympanic is like the cartilaginous pinna of the human 

 ear, but without a tubular meatus. Continuous with 

 the periotic is an ovoid projection which occupies a con- 

 cave surface in the squamous temporal. The periotic, 

 consisting of dense bone, is 2 inches in its longest 

 diameter. The chain of ossicles has been removed from 

 the tympanic cavity and is figured to the right of 

 the outer surface of the tympano-periotic. 



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