340 TESTACEA ATLANTICA. 



equally certain, from its general contour and coloration, its 

 blackened, highly-polished aperture, its total freedom from an 

 umbilicus, and the minute spired lines of its surface, that it 

 belongs strictly to the lactea group. 



If the sample now before me be a normal one of its kind, the 

 H. gibboso-basalis differs from the lactea in its very much 

 smaller size (its greatest diameter being only 12 lines, instead of 

 about 20) and its comparatively dark or subconcolorous sur- 

 face, — which is entirely free from pallid specks or freckles, 

 appearing at first sight (at any rate when viewed from above) 

 to be of an almost uniformly livid- or plumbeous-brown ; though 

 when more closely inspected, it will be seen, in reality, to be of 

 a dull, dirty, yellowish-tinge (as is evident about the umbilical 

 area and outside the aperture), but with four darker bands so 

 obscure and diffused that on the upper side they are well-nigh 

 indistinguishable, — nearly blending together (particularly on. the 

 anterior region of the basal whorl) so as to tone-down, or infus- 

 cate, the entire surface. 



Apart however from contour and size, the present Helix has 

 the spire (which is composed of a volution less) more obtuse 

 than in the H. lactea, its aperture is relatively smaller and less 

 deflexed, its peristome is very much less expanded or developed, 

 its sculpture is altogether finer, and there are a few abbreviated 

 grooves and ridges, far within the aperture, on the ventral wall 

 of the body-volution. But a more curious feature (if indeed it 

 be a constant one) consists in the uneven, or biflexuose, nature 

 of the columellary portion of its lower lip, — occasioned by an 

 unusual prominence, or gibbosity, amounting almost to a large 

 obtuse tubercle or lump, at a little distance from the insertion 

 of the latter into the axis. This last-mentioned feature, if not 

 a mere accidental one, is at least very remarkable. 



Whether the H. gibboso-basalis is in any way related to 

 the H. Dupotetiana, Terver {Pfeiff., Mon. Hel. i. 274), from 

 Northern Africa, with the diagnosis of which it has certainly 

 something in common, I have no means of deciding. 



(§ Hemicycla, Sow.) 



Helix gravida. 



Helix gravida, Mouss., Faun. Mai. des Can. 85 (1872) 



55 



Pfeiff., Mon. Hel. vii. 343 (1876) 



Habitat Fuerteventuram ; a Dom. Fritsch semifossilis re- 

 perta. 



I have had no opportunity of inspecting this large Helix, 

 which appears to be somewhat intermediate between the sar- 



