Zoological Society. 475 



and this again into the cementum, without offering any generic pecu- 

 liarities. 



The cementum is in no part of the fang very abundant, as com- 

 pared with the amount which is found in the teeth of many other 

 animals. Near the neck of the tooth it is arranged in minute rods 

 or columns, similar to that which I have described as existing in the 

 teeth of many Rodents. In this situation it is destitute of lacunae ; 

 but in tracing it downwards towards the root of the tooth, where it 

 is increased in quantity, lacunae possessing the usual characters are 

 found. In addition to the lacunae the cementum is traversed in parts 

 by ill-defined canaliculi, which proceed from the surface of the fang in 

 tolerably straight lines. 



In tracing a longitudinal section of a molar tooth downwards from 

 the crown to the end of the fang, it will be seen that at places the 

 dentine has been removed and the space filled up vrith cementum. 

 Here and in other parts the cementum is abundantly supplied with 

 vascular canals. 



The enamel does not differ in any material points from that of the 

 teeth of Ruminants. The fibres have a minutely granular appearance 

 and have a diameter of about the 5000th of an inch. On the sides 

 of the tooth they pursue an outward com'se, and make one bold curve, 

 the convexity of which is directed towards the masticating surface, 

 while on the crown of the tooth their course is waved and irregular ; 

 an arrangement which no doubt adds much to the strength of the 

 tissue in that part where the greatest strength is required. 



In the incisor teeth similar peculiarities may be observed, but they 

 are much less strongly marked than in the molar teeth. A'^ascular 

 canals are, too, of less frequent occurrence in the incisor teeth. 



I hope on a future occasion to be enabled to lay before the Society 

 a statement of the peculiarities which pertain to and are characteristic 

 of other groups of animals. 



2. Description of a new genus of Bivalve Shells, and a 



Sea Egg, from Nevf Zealand. 



By J. E. Gray, Esq,, F.R.S., P.B.S. etc. 



Mr. Richard Taylor, of Wanganui, New Zealand, has kindly sent 

 to the British Museum a series of marine and freshwater shells, col- 

 lected by him in 1847. Among many other interesting specimens is 

 one which combines the form and internal appeaiance of a Solen with 

 the hinge-characters of a Mactra, and evidently forming the type of a 

 genus not hitherto observed. It may be thus named and character- 

 ized : — 



Vanganella. 



Shell equivalve, oblong, transverse, thin, compressed, rounded be- 

 hind, rather produced and tapering in front, covered with a thin, 

 hard, polished periostraca ; the inner surface of each valve straight, 

 with two diverging, thickened ribs just within the stars of the ab- 

 ductor muscles, which are large and far apart, and the upper front 



31* 



