Manchester Memoirs, Vol. lv. (191 i), No. 18. 7 



three sub-equal divisions by rounded ridges running 

 longitudinally ; the outer grooves lodge the alveoli, of 

 which 10 are visible on the right side, they are very large, 

 averaging 2cms. in diameter. The central division is a 

 deep channel, which is anteriorly divided by a slight 

 rounded median ridge. 



The specimen described above is obviously a Metno- 

 rhynchus, and in its great solidity and relatively broad 

 snout is only comparable to three described species : — 



Metriorhynchus brachyrhynchus, Deslongchamps. 

 M. hasti/er, „ 



M. palpebrosus, Phillips. 



Comparison with the figures and descriptions of 

 M. brachyrhynchus given by Deslongchamps and Leeds 

 and with the specimens in the British Museum and that 

 at Caen, shew that the specimen under consideration 

 cannot be referred to this species. 



In M. brachyrhynchus the snout tapers more rapidly, 

 the nasals are narrower anteriorly and broader posteriorly, 

 the distance separating the nasals and pre-maxillae is 

 smaller, and the palate is not so profoundly channelled 

 as in our specimen. On the other hand, the number of 

 teeth may have been similar. 



The fragment appears to agree with M. palpebrosus 

 in the gradual narrowing of the snout, and in the fact that 

 the nasals never form the widest part in a transverse 

 section of the skull. There are, however, 18 alveoli in 

 M. palpebrosus in a space corresponding to 10 in our 

 specimen, and the palate does not shew the very markedly 

 channelled form which is so characteristic of our fragment. 



M. hastifer differs from our fragment in the following 

 characters : — 



