MADEIRAN GROUP. 161 



tively flattened under-region generally ornamented with one or 

 two (sometimes obsolete, and occasionally confluent) fasciae. 



The H. echinulata, which is less abundant, on the whole, 

 than the bicarinata, is locally common on the mountains of 

 Porto Santo ; and, although not easy to separate at the time of 

 capture from its ally (an after-examination being absolutely 

 necessary for that purpose), I believe that it is more often on the 

 Pico Branco that we have met with it, than elsewhere. 



The Baron Paiva records the H. echinulata in a subfossil 

 state ; but, although this is not by any means unlikely, I have no 

 evidence myself that it has yet been observed in any of the cal- 

 careous deposits ; though its comparatively gigantic analogue 

 (enunciated above as the H. echinoderma) is met with occa- 

 sionally, and it is not impossible therefore that that particular 

 form was regarded by the Baron as sufficiently identical with 

 the recent type. 



Helix bicarinata. 



Helix bicarinata, Sow., Zool. Journ. i. 58. t. 3. f. 7 (1825) 

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



f. 30(1831) 



bicarinata, Pfei/., Mon. Hel. ii. 190 (1848) 

 Lowe, Proc. Zool. Soc. Lond. 186 (1854) 



Alb., Mai. Mad. 36. t. 9. f. 1-4 (1854) 



Paiva, Mon. Moll. Mad. 45 (1867) 



Habitat Portum Sanctum ; sub lapidibus vulgatissima. In 

 statu semifossili parce (sub forma ' var. /3. auctaj Woll.) re- 

 peritur. 



So closely does the present little Helix resemble the H. 

 echinulata, that I am far from certain that it is more in reality 

 than a phasis of that species with a double keel ; and this is all 

 the more possible from the fact that a bi- and simply carinated 

 state are by no means uncommon in many Helices. Yet the 

 two forms are so readily separable (for I have never found a 

 single example, out of many hundreds I might almost say 

 thousands which I have inspected, which could be regarded as 

 strictly intermediate), that I prefer, inasmuch as they have 

 already been published under different names, to treat them as 

 distinct. The Baron Paiva, in his late Monograph, ias assumed 

 them to be conspecific, and it is quite open to any naturalist to 

 adopt that opinion if he pleases ; but since it is scarcely possible 

 that the qucestio vex-ata can ever be absolutely settled, I would 

 rather, for my own part, acknowledge them under the titles 

 which they have so long received, than run the risk of error in 

 a speculation which is perhaps unsolvable. 



With these remarks I think it sufficient to add, that the H. 



