( 92 ) 



PosTEEioR Cardinal Vkin. 



Dr. Dobson does not mention the condition of the azygos or posterior cardinal 

 veins in Centetes. It may, therefore, be worth while to note that in this Insectivore 

 there is bnt one azygos, the right, instead of two as in the Hedgehog. This vein 

 is large, and extends back as far as the diaphragm, and farther ; bnt unfortunately 

 I was nnable to detect its connection, if any, with the vena cava posterior. 



The Skull. 



After the exhaustive descriptions of Mivart,* Dobson, f and Parker, t I have 

 not, as might be expected, much to add to our knowledge of the skull of Centetes. 

 There is, however, one point to which attention does not appear to have been 

 directed by any one of the authors quoted. 



The single nasal bone is described by Dobson in the following words : " The 

 nasals are united, even at birth, but slightly separated in front, extending backwards 

 as a narrow process between the froutals as far as a line connecting the anterior 

 margins of the orbits." This description agrees accurately with what I have seen ; 

 bnt it is not quite suflScient to describe all that is visible when the skull is further 

 dissected. The posterior extremity of the nasal appears in the uninjured skull to 

 die away at the point mentioned by Dr. Dobson, where the two froutals come into 

 contact in the middle line. These bones, I may observe in passing, are a little 

 asymmetrical, the left frontal slightly overtop])ing the right. When the froutals 

 are divided by a vertical cut, the bones (fig. 3) are seen to lie above a triangular- 

 shaped piece of bone {i.e. triangular in transverse section), and thus not to roof in 

 of themselves the olfactory region. The piece of bone which underlies them is the 

 apparent continuation of the nasal, and can be traced ibr a considerable way back, 

 lining the roof of the skull. I am inclined to think, however, that this tract of bone 

 is not merely the nasal overlapped by the froutals. It is impossible, with the 

 material at my disposal, to be positive n]ion the point : but I am rather disposed to 

 regard it, and perhaps the posterior jiart of the nasal which is exposed on the upper 

 surface of the skull, to be an ossified portion of the mesethmoid, which in this 

 animal, as in the whales and in certain struthious birds, comes to lie partly upon 

 the surface of the skull. 



The accompanying sketches (Figs. 3, 4) will show the arrangement of the bones 

 which obtains, and it explains itself. 



» Joim. Anat. Phyn. ii. (1868), p. 117, and P.Z.S. 1871, p. 72. 



f Loc. cit. p. 72. 



X Phil. Trmu. 1885, p. 218. 



