318 TEST ACE A ATLANTIC A. 



Mousson treats this shell as a P alula, associating it (under 

 his section Lyra) with the Lanzarotan H. torrefacta, Lowe ; 

 but I cannot agree with him in either of these steps. For, in 

 the first place, the minute spiral lines on which he rightly lays 

 so much stress exist also, though very obscurely, in the H. lenis 

 of Shuttleworth, which is most unmistakeably (and by his own 

 admission) a Hyalina, and much more conspicuously in a new 

 species * which is so closely allied to the H. lenis that it is but 

 just separable from it; whilst the affinities of the H. torrefacta 

 are, in my opinion, with the Madeiran H. lentiginosa, Lowe, 

 a form which is far removed from the whole of these imme- 

 diate groups. Both Shuttleworth and Mousson, indeed, would 

 appear to have completely overlooked in the H. lenis the 

 existence of these "spiral lines" on which the latter has 

 founded his section Lyra, and which, although usually very 

 difficult to detect, I find to be quite appreciable (but often 

 fragmentary) in about one specimen in every twenty ; whilst (as 

 just mentioned) in an intimately related form which was taken 

 by Mr. Lowe at Osorio, on the mountains of Grand Canary (and 

 which I at first imagined might represent but an insular 

 phasis of the one from Palma and Hierro), the spiral lines are 

 as strongly developed as in the H. circumsessa. Hence I think 

 there can be no question that the circumsessa, osoriensis, and 

 lenis are intimately bound together by the very peculiar and 

 significant character to which I have just called attention ; and 

 since there cannot be the slightest doubt that the second and 

 third of these are true Hyalinas (being in point of fact, very 

 manifestly akin to the common H. cellaria, Mull.), it follows 

 that the circumsessa must be regarded as a Hyalina likewise, 

 and not as a Patula. 



The H. circumsessa is, on the average, a trifle smaller and 

 darker than the H. osoriensis, its spire is a little more de- 

 pressed, the basal volution is (relatively) not quite so broadly 

 developed, its umbilicus is appreciably wider (or more open), 

 and its minute spiral lines are rather more numerous, or set 

 closer together. It is an essentially characteristic species in 

 Teneriffe, which appears to be its chief habitat ; indeed it was 

 not met with by either Mr. Lowe or myself in any of the other 

 islands, though it is recorded to have been taken by both 

 Blauner and Fritsch in Palma. In Teneriffe however it is 

 abundant throughout the sylvan districts of an intermediate 

 altitude, where we obtained it at the Agua Garcia, at Las 

 Mercedes, in the wooded region above Taganana, and even 

 (though more sparingly), at a lower elevation, around both 

 Garachico and Sta. Cruz. 



1 The If. osoricnsis, Woll., enunciated below. 



