266 Rev. L. Jenyns on some of 



In a second specimen, however, of the S, tetragonurus the 

 number of caudal vertebrae was as many as 16, whilst in a 

 second of the B, Hibernicus it was only 14 ; thus showing 

 that in each species it is subject to some variation. 



In the above table I have estimated the number of sacral 

 vertebrae as 2, according to Duvernoy, who, though he has 

 not given the entire number in the column, has noticed the 

 very peculiar and elongated form of these two, having a sharp 

 ridge on their upper surface, much developed, and common 

 to them both. It is evident, however, on a close inspection, 

 that the first of these two vertebrae, which he speaks of as 

 being the most elongated, is resolvable into 4, which are 

 more or less consolidated together, according to the age of 

 the individual. In some instances the lines of separation 

 between them are so distinct, that they might be counted 

 separately ; in which case the entire number of vertebrae in 

 the S. tetragonurus would stand at 47 or 48, and in the S. 

 Hibernicus at 46 or 47. 



I have deemed it of importance to mention these facts with 

 respect to the vertebrae, from the circumstance of M. de 

 Selys-Longchamps having found it a valuable character in 

 distinguishing some closely allied species of Arvicola, and 

 observed to me that he thought it might prove of equal ser- 

 vice in helping to discriminate those of the genus Sorex. It 

 appears, however, from what has been stated, that the exact 

 number in the tail, in this instance, cannot be relied on. 



(6.) Sorex castaneus (Ann. Nat. Hist., vol. ii. p. 43). — 

 I have not been able to obtain any more specimens of this 

 species*, and can therefore say nothing further as to its being 

 really distinct from the S, tetragonurus, M. de Selys-Long- 

 champs, who has paid so much attention to this genus, and 

 to whom it was shown during his visit to London in 1839, 

 declined giving any decided opinion about it; at the same 

 time, he observed that he had never seen any individuals of 

 the S, tetragonurus of so rufous a tint. I conceive, however, 

 that the fact of a male and female having been found together, 

 the latter of which was big with young when taken, rather 

 tends to support the idea of its being distinct. Also, in- 

 dependently of its colour, and one or two other external 

 peculiarities, there is a slight difference observable in the 

 cranium, as already pointed out in a former paper f. 



* The original specimens were not obtained in my own immediate neigh- 

 bourhood, nor by myself, but in a fen distant some miles from me, and by a 

 person who has since left the district; and I am ignorant of the exact locality 

 in which he met with them. 



t Ann. N. H., vol. i. p. 424. 



