760 Proceedings of the Royal Society 
for a supplementary tooth, although none protruded from it. In 
the young male a minute denticle was seen at the bottom of this 
socket. 
He then described a dissection he had made of the upper jaw of 
a male foetus, 74 inches long, given him by Mr C. W. Peach, in 
which, imbedded in the gum on each side, were two well-formed 
dental papillae, barely visible to the naked eye. Each papilla was 
contained in a well-defined tooth sac. Calcification of the papillae 
or of the wall of the tooth sac had not commenced. The minute 
structure of these embryonic teeth was next described. The more 
anterior of the two papillae was T 2 oths inch behind the tip of the 
jaw, and the more posterior lay about y^th inch behind the 
anterior. 
No rudimentary teeth were found in the lower jaw. 
The formation of bone had only just begun in the fibrous matrix 
of the maxillary bones ; hut in the lower jaw a very decided ossifica- 
tion of the fibrous membrane investing the cartilage of Meckel had 
commenced. 
3. On the occurrence of Ziphius cavirostris in the Shetland 
Seas, and a comparison of its Skull with that of Sowerby’s 
Whale ( Mesoplodon Sowerhyi). By Professor Turner. 
This paper contained a brief historical sketch of Ziphius cavi- 
rostris. The skull of a specimen caught at sea in 1870, off Hamna 
We, Northmaven, Shetland, was then described, and this skull was 
compared with previously recorded specimens. A brief historical 
sketch of Sowerby’s whale was then given, a skull in the Edinburgh 
Museum of Science and Art was described, and reasons were 
advanced for associating it with the genus Mesoplodon rather than 
with Ziphius. 
4. On the Maternal Sinus Vascular System of the Human 
Placenta. By Professor Turner. 
The author gave a brief sketch of the various theories which 
have been advanced by Velpeau, R. Lee, Braxton Hicks, the 
Hunters, Owen, Weber, J. Reid, J. Groodsir, Virchow, Kolliker, Van 
