MADEIRAN GROUP. 191 



Helix Delphinula, Lowe, Cambr. Phil. S. Trans, iv. 64 



[note] (1831) 



Id., Ann. Nat. Hist. ix. (1852) 



Id., Proc. Zool. Soc. Lond. 193 (1854) 



Alb., Mai. Mad. 80. t. 17. f. 1, 2 



(1854) 



Pawa, Mon. Moll. Mad. 66 (1867) 



Habitat Maderam, semifossilis ; in arenis calcareis juxta 

 Canipal vulgaris, hodie recens hactenus baud observata. 



Of all the subfossil Helices of tbe archipelago, the some- 

 what large and singular H. delphinula (which measures from 

 about 9 to 1 1 lines across its broadest part, and which is pecu- 

 liar to the calcareous deposits near Canical) is by far the most 

 remarkable one which has not yet been discovered in a recent 

 condition. It is not unlikely however that more careful re- 

 searches in some of the less-known ravines towards the north- 

 east of the island may still establish it as a member of the 

 present fauna, just as the equally wonderful //. delphinuloides, 

 which had escaped the united observations of so many natu- 

 ralists through more than half a century, was detected so lately 

 as in 1860, by Mr. Lowe, at the edges of the new Levada which 

 has opened-out a previously unexplored district in the Bibeira 

 do Fayal. That it must have been once extremely common is 

 evident from the great abundance in which it now exists in the 

 sandy, subfossiliferous beds near Canipal, where it may be 

 said, perhaps, to take the place in Madeira proper of the 

 nevertheless very dissimilar (though in some respects analo- 

 gous) H. tectiformis of Porto Santo. 



From only subfossil specimens it is not easy to say what the 

 exact colour of the H. delphinula may have been when in a 

 living state; but judging from the analogy of the H. tecti- 

 formis, as well as of the H. delphinuloides and of the various 

 other members of the section Coronaria, we may be well-nigh 

 certain that it was either a calcareous-white or nearly so. But, 

 apart from all considerations of hue, the H. delphinula (which 

 has something in common with the H. turcica, Chemn., from 

 Morocco) may be known by its somewhat lenticular outline, 

 but nevertheless cu>oa-shaped, extremely obtuse spire ; by its 

 horizontally-expanded, more or less foliaceous, tectiform keel 

 (which is traceable up the majority of the whorls, overlapping 

 the suture like a narrow plate); and by its enormous but abruptly 

 scooped-out umbilicus, which is not only spirally visible to the 

 extreme apex, but has its sides coarsely sculptured with con- 

 centric spiral costse (decussated by irregular, undulating, lighter 

 transverse ones) similar to those which roughen the entire 

 inferior surface (except the lamina-like keel) of the basal volu- 



