AZOREAN GROUP. 51 



than a state of the common Madeiran A. aiqualis, in which the 

 outer lip of the peristome is thickened internally into a central 

 denticle, and in which the impressed spiral lines which are so 

 often traceable (more especially towards the base) in that spe- 

 cies happen to be more than usually evident. Judging from 

 an immense series of the A. cequalis which I have lately over- 

 hauled, composed of nearly two thousand specimens, I find that 

 these particular features on which the A. Vulcani was made to 

 rest are liable to be gradually assumed by every phasis of the 

 shell, and moreover to an equal extent, and that consequently 

 they possess no kind of specific significance whatsoever. Indeed 

 I have examples in which they are so rudimentary as to be barely 

 appreciable, and others in which they are more and more ex- 

 pressed until they become comparatively conspicuous ; and as for 

 the somewhat 'slenderer' outline of the A. Vulcani, I will 

 merely add that the individuals from the Salvages are almost 

 invariably a trifle narrower and more elongated than those from 

 Madeira, and yet they pass so completely into the ordinary type 

 that it is impossible to regard them as representing more than a 

 very slightly modified local race of the universal Madeiran shell. 

 Whether the strictly normal aspect of the A. cequalis, however, 

 is met with at the Azores, or whether all the examples have the 

 right-hand margin of the aperture thus incrassated, I have no 

 means of deciding. In all probability the examination of a 

 sufficiently long array of specimens would bring to light the ex- 

 istence (as in Madeira) of both varieties. 



Auricula gracilis. 



Melampus gracilis, Lowe, Zool. Journ. v. 288 (1835) 

 Auricula gracilis, Id., Proc. Zool. Soc. Lond. 217 (1854) 

 „ vespertina, Morel., Hist. Nat. des Acor. 210. t. 5. 



f. 9 (1860) 

 „ „ Drouet, Faun. Agar. 169 (1861) 



Alexia Loweana, Pfeiff., Mai. Blatt. xiii. 145 (1866) 



„ „ Paiva, Mori. Moll. Mad. 154 (1867) 



Auricula denticulata et Loweana, Wats., Journ. de Conch. 



220 (1876). 



Habitat Pico ; per litora maris, inter rejectamenta, parce 

 (emortua) reperta. 



Several examples of this Auricula are stated by Morelet to 

 have been found (dead), amongst rejectamenta,, on the sea-shore 

 in Pico ; and the excellent figure given by him, accompanied by 

 the equally good diagnosis, leaves no doubt whatever on my 

 mind that his ' A. vespertina ' (which is the title under which 

 he describes the species) is identical with the A. gracilis, of 



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