84 TEST-ACE A ATLANTIC A. 



and more numerous volutions, and in the coarser, fewer, and 

 more elevated costae (or folds) of its upper surface. 



Indeed the present Patula (so far as I am able to judge 

 from colourless and subfossilized examples) so nearly resembles 

 the Madeiran P. Guerineana that it might well-nigh be sup- 

 posed, at first sight, to represent but the quondam phasis of 

 that species. When accurately looked at, however, it will be 

 seen to possess a few differential characters of its own which 

 will suffice to stamp it as a perhaps truly distinct, though 

 proximate, member of the same local assemblage. Thus it is 

 not only a little less flattened both above and below (the spire 

 being just appreciably less depressed, and the under portion of 

 the basal whorl conspicuously broader, convexer, and more de- 

 veloped), but its umbilicus is not quite so wide at the com- 

 mencement, its keel is less pronounced (or somewhat more 

 obtuse), and the costae of its upper surface are not only still 

 more elevated and regular, but likewise appreciably less ob- 

 lique, being more at right angles to the suture. What its 

 colour may be, when in a recent condition, I have no means of 

 deciding. 



Patula Guerineana. 



Helix Gruerineana, Lowe, Ann. Nat. Hist. ix. 115 (1852) 

 semiplicata, Pfeiff., Mai. Blatt. 63 (1852) 

 Id., Mon. Hel. iii. 114 (1853) 



Guerineana, Lowe, Proc. Zool. Soc. Lond. 176 (1854) 

 semiplicata, Alb., Mai. Mad. 19. t. 2. f. 1 1-1 4 (1854) 

 Paiva, Mon. Moll. Mad. 80 (1867) 



Habitat Maderam ; in sylvaticis intermediis rarior, sub 

 foliis marcidis necnon in humidis latens. 



This is one of the most elegant of the Madeiran Land- 

 Shells, its flattened, discoidal contour, added to its enormous 

 umbilicus, its highly polished (and obliquely, though very 

 obscurely, subfasciated ) under-region, and the beautifully varie- 

 gated hue of its coarsely costate volutions (which seem to be 

 striped with alternate, but unequal, transverse bands of a lively 

 reddish-brown and of a dirty whitish-yellow) giving it an 

 appearance which it is impossible to mistake. Until lately it 

 has been regarded as the Madeiran representative of the 

 common European P. rotundata, Mull. ; but, as already shown, 

 it belongs to a rather different type, characterised by its more 

 numerous, narrower, and strongly costate whorls, by its brightly 

 polished, nearly unsculptured inferior portion, and by its still 

 larger umbilicus. And, apart from these points, it is more de- 

 pressed, and (on the average) a trifle larger, than the P. rotun- 

 data, and its keel is sharper. Added to which, the latter 



