614 TEST ACE A ATLANTIC A. 



just separable from) the 'var. ft. anconostoma* which is so 

 widely spread throughout the other Atlantic archipelagos, were 

 I not unwilling to suppress a species which has already been 

 proposed by so able a conchologist as Dr. H. Dohrn. But 

 when we bear in mind that the P. umbilicata (as represented 

 by its ' var. ft. anconostoma ') has found its way to the Azores, 

 the Madeiras, the Canaries, and even to St. Helena, and that it 

 is eminently variable, both in outline and exact colour, and 

 slightly so even in the development of its aperture and plait, it 

 seems to me that the very trifling differential characters which 

 separate the present Pupa from it might reasonably be looked 

 upon as mere geographical ones indicative of a region so remote 

 as the Cape Verdes. Still since it possesses a character or two 

 (barely appreciable, however, in the ' var. a. perdubia ') which 

 a very careful observation will just enable us to recognize, I 

 think perhaps that I have a sufficient excuse (even though 

 contrary to what my own mode of treatment would have sug- 

 gested) for retaining Dohrn's species (the title of which however 

 has been altered by Pfeiffer, on account of ' Milleri' having 

 been preoccupied, Mai. Bldtt. xiv. 129, for a Pupa from the 

 Bahama Islands) as distinct. 1 



After a very careful comparison of the P. Dohrni with a 

 long series from Madeira, the Canaries, and St. Helena of the 

 6 var. ft. anconostoma ' of the P. umbilicata, I can detect no 

 other points on which to uphold it as separate, except that the 

 entire shell is, on the average, just perceptibly more ovate (or 

 widened posteriorly), with its aperture perhaps somewhat larger 

 and more obtusely rounded below, with its outer lip a trifle 

 more upwardly produced on the basal volution, and with its 

 ventral plait more backwardly (or internally) prolonged. But 

 in every other respect it seems to me to be undistinguishable 

 from its ally. 



Having therefore expressed my opinion concerning the spe- 

 cific value of the few distinctive features which are supposed to 

 characterize the present Pupa, I will merely add that it was 

 met with by Dr. H. Dohrn (though sparingly) in the Eibeira de 

 Joao Affonso in S. Antao, and by Mr. Lowe in S. Nicolao ; but 



1 Dohrn was aware that the title ' Milleri ' had already been employed by 

 Pfeiffer for a Pupa ; but as he considered that Strophia (the particular group 

 which embraces Pfeiffer's West-Indian species) is generically distinct from 

 Ennea [or Gastrodon, Lowe], which contains the Cape Verde one, he deemed 

 it unnecessary to alter the name which he had selected. Still, whatever be 

 the ultimate genera within which these two forms may be made (respectively) 

 to repose, it is certain that the laws of nomenclature will not admit of two 

 distinct species being even published under absolutely the same title ; and if 

 one of them, therefore, must be withdrawn, we have no choice but to act in 

 accordance with the rule of priority. 



