MADEIRAN GROUP. 201 



In outline the H. tiarella differs from all the other 

 members of the Coronaria and Craspedaria sections in the 

 fact of the cupola-shaped, apically-obtuse spire being very much 

 'more raised ; and it is also less decidedly colourless than any of 

 them, for, although often (when in even a living state) scarcely 

 more than of a dull chalky-white, it has far more frequently a 

 more or less brownish tinge, the ribs and other prominences being 

 paler, which gives the entire surface a very beautiful and em- 

 bossed appearance. The short radiating ribs on the anterior 

 zone of its ultimate and penultimate volutions are exceedingly 

 conspicuous, whilst the posterior zone has the spiral costse ex- 

 tremely coarse, broken-up, irregular, subconfluent, and frag- 

 mentary, a peculiarity of sculpture which obtains equally on 

 the basal portion of the shell, where there are also scarcely any 

 traces (except at the entrance of the actual umbilicus) of the 

 radiating transverse lines which are more or less evident in the 

 allied species. Its umbilicus, too, is almost (in part) overhung 

 by the largely expanded edge of the circular and much raised 

 peristome, which is not the case in any of the preceding mem- 

 bers of the group. 



( Lemnistiay Lowe.) 



Helix Michaudi. 



Helix Michaudi, Desk., in Encycl. Meth. ii. 263 (1830) 

 bicolor, Lowe, Cambr. Phil. S. Trans, iv. 58. t. 6. 



f. 22 (1831) 



Michaudi, Pfeiff., Man. Hel. i. 157 (1848) 

 Lowe, Proc. Zool. Soc. Lond. 170 (1854) 



Alb., Mai. Mad. 21. t. 2. f. 36-38 (1854) 



Paiva, Mon. Moll. Mad. 69 (1867) 



sent, and that the species has no kind of claim to be regarded as even extra- 

 Madeiran. Under these circumstances it is much to be regretted (as indeed 

 I have already mentioned at p. 131 of this volume) that Mousson should have 

 admitted it, as well as the H. tceniata, into his late monograph of the Cana- 

 rian Land-Mollusca ; for to perpetuate, however unintentionally, a glaring 

 geographical error (even though qualified by remarks as to the uncertainty of 

 the habitat) seems to me to be scarcely counterbalanced by the adding of two 

 additional species to augment a local list. My own belief is, that the ff. 

 tiarella does not occur beyond the limits of the central island even in the 

 Madeiran archipelago ; and I look therefore with unbounded suspicion on the 

 Baron Paiva's brief remark 'rarissima ad Zimbral d'Areia in Portosancto 

 insula,' because no other naturalist has yet observed it in the Porto-Santan 

 deposits, and the repeated visits of Mr. Lowe and myself (extending to four 

 and five weeks at a time) to that island, during which the examination of the 

 calcareous beds was one of our primary objects, never revealed so much as a 

 vestige of this species which is so abundant in Madeira proper ; whilst, at the 

 same time, the extreme looseness, as regards habitat, of the Baron's material 

 (which was seldom, if ever, collected by himself) I have had occasion more 

 than once to touch upon. 



