- , I TJSS TAt EA A TL ANTIC A. 



Director of the Lisbon Museum, finds abundantly, in stagnant 

 water, tanks, &c, everywhere, a shell precisely identical. Ex- 

 amples from Cintra, kindly communicated by this able na- 

 turalist, perfectly agree with these Madeiran specimens, one of 

 which is remarkable for exhibiting faint traces of spiral stria- 

 towards the peristome on the under (or lower and more concave) 

 side of the shell, — invalidating thus far the specific difference, 

 which has been indeed already called in question (see 'Gray's 

 Man.,' 260; though compare also 'Forbes & Hanley, Brit. 

 Moll.'' iv. 151) between the P. glaber, Jeffr., and the P. albus, 

 Miill.' 



Genus 21. ANCYLUS, Geoffr. 



Ancylus striatus. 



Ancylus striatus, Quoy et Gaim., Voy. de VAstrol. iii. 207. 



t. 58. f. 35-38 (1833) 

 „ „ W. et P., Ann. des Sc. Nat. 28. Syn. 323 



(1833) 

 „ aduncus, Gould., Proc. Bost. Soc. N. H. ii. 210 



(1848) 

 „ fluviatilis, Lowe [vix Miill., 1 774], Proc. Zool. Soc. 



Lond. 218 (1854) 

 „ aduncus, Alb., Mai. Mad. 74. t. 16. f. 37, 38 (1854) 

 „ fluviatilis, Paiva, Mon. Moll. Mad. 148 (1867) 

 „ striatus, Mouss., Faun. Mai. des Can. 141 (1872) 

 „ fluviatilis, Watson, Journ. de Conch. 224 (1876) 



Habitat Maderam ; in aquis fiuentibus (prsecipue editiori- 

 bus) ubique vulgaris. 



Whether this Ancylus, which is so abundant in the streams 

 of intermediate and lofty elevations throughout Madeira proper, 

 is more in reality than a geographical phasis (as indeed it was 

 regarded by Mr. Lowe) of the common European A. fluviatilis, 

 I am extremely doubtful ; nevertheless since it does certainly 

 differ somewhat, at any rate in sculpture, from the more 

 northern type, and it appears to me to be absolutely undistin- 

 guishable from the universal species of the Canarian archipelago 

 (which has been acknowledged by various monographers under 

 the name of striatus), I have no hesitation in citing it accord- 

 ingly, — and that too even whilst admitting (as just implied) 

 that it may perhaps represent but a local modification of its 

 widely-spread European analogue. 



Being extremely inconstant in stature, I cannot perceive 

 that this Madeiran Ancylus is larger (as was asserted by Mr. 

 Lowe, and after him by the Baron Paiva) than the ordinary 

 A» fluviatilis ; but it is unquestionably a trifle more powerfully 



