274 TEST ACE A ATLANTIC 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 striae 

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



Genus 21. ANCYLTTS, Qeoffr. 

 Ancylus striatus. 



Ancylus striatus, Quoy et Gaim., Voy. de I' Astral, iii. 207. 



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

 W. et B., Ann. des Sc. Nat. 28. Syn. 323 



(1833) 

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



(1848) 

 fluviatilis, Lowe [vix Mull., 1774], 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 fluentibus (prascipue 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 un distin- 

 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 



