MADEIRAN GROUP. 141 



from that species by being not only more globose both above 

 and below, with its umbilicus almost (or, more often, entirely) 

 closed up by the expanded lamina of the lower lip, but likewise 

 by its ventral plait being obsolete, and the aperture narrower 

 and very differently shaped, in fact somewhat semi-lunate, in- 

 stead of subcircular, with the peristome broadly interrupted 

 (instead of being sub-continuous) across the body-volution, and 

 the labra themselves nearly parallel. 



I may observe that a single mutilated example which may 

 possibly belong to the H. arcinella was found by Mr. Lowe in 

 Porto Santo, namely at the Fonte d'Areia, in 1828; but as it 

 seems to me to differ a little from the Madeiran type, in being 

 somewhat more granulated below and with its ventral plait 

 more appreciably developed, I think it safer until further mate- 

 rial has been obtained not to record the H. arcinella as Porto- 

 Santan, seeing that it is not impossible that this broken 

 specimen may in reality prove to be the exponent of some closely 

 allied species, as yet un characterised. 



Helix arridens. 



Helix arridens, Lowe, Cambr. Phil. S. Trans, iv. 43. t 5. 



f. 9 (1831) 



Pfei/., Mon. Hel. i. 217 (1848) 



Lowe, Proc. Zool. Soc. Lond. 180 (1854) 



Alb., Mai. Mad. 39. t. 9. f. 23-26 (1854) 



Paiva, Mon. Moll. Mad. 29 (1867) 



Habitat Maderam ; in intermediis praecipue occurrens, 

 vulgaris. 



The members of the section Rimula, which include the 

 present species, the preceding one, and the following three,- - 

 have their umbilicus either nearly or altogether closed over by 

 the outwardly expanded lamella of the lower lip ; and they are 

 all of them rather small in stature, and more or less clothed 

 (though it is impossible to assert this absolutely of the H. arci- 

 nella, which is known only in a subfossil and decorticated state) 

 with squamiform hairs, or hair-like lacinise. 



The H. arridens is decidedly the commonest of this particu- 

 lar type, it being generally distributed over the intermediate 

 regions of Madeira proper, to which island it seems to be pecu- 

 liar. Like the H. lentiginosa it is often abundant under the 

 dried and brittle leaves of the Semperviva which stud the faces 

 of the rocks in the shady ravines ; but it is almost equally to be 

 found in other situations, as, for instance, about the roots of 

 plants, and amongst detritus, on the ledges of the rocks, and 

 beneath the dead and loosened bark of the old laurels. Under 



