HELIX. R 361 
Helix leucas. 
Miiller, Schréter, Gmelin, and Dillwyn have alike been frus- 
trated in the determination of a species whose brief diagnosis 
neither presented any salient character nor was aided by any 
reference to an illustrative figure. Férussac placed it as an 
uncertain species between cicatricosa and the levipes of Miiller ; 
Menke, in his Synopsis (p. 24), cited the albella of Chemnitz 
(vol. ix. p. 87, pl. 126, f. 1105, 1106) as identical; the latter was 
intended by the author of the ‘Conchylien Cabinet’ for the 
albella of Linneeus. 
Having perceived by his catalogue that Linnzus possessed 
the H. lewcas, I carefully scrutinised each snail in his collection, 
and at length observed a paper in which were deposited certain 
specimens that exactly coincided with the description, which, 
moreover, was scarcely approached by any other Helix in the 
cabinet. These shells were young individuals of the H. Pisana 
of Miiller (Draparn. Moll. France, pl. 5, f. 14, 15), and were in 
all probability the originals of the description. In this instance 
the figure mentioned by me as illustrative is that of an adult 
shell, and not a portrait of the Linnean examples: it was not 
thought worth while to delineate them, since Pisana is too well 
known to be mistaken by even a tyro in conchology. Their 
presence confirms the conjecture so skilfully hazarded by 
Dr. Pfeiffer. 
Of course the well-established name of Miiller should not be 
affected by this identification; since no conchologist, without 
actual examination of these specimens, could have ascertained 
what the illustrious Swede intended by his H. leucas. 
Helix planorbis, 
Of the shells in the Linnean collection only two, the Planorbis 
carinatus and the P. marginatus of Draparnaud (Moll. France, 
pl. 2, f. 11 to 16), sufficiently harmonise with the characteristics 
and synonymy of this species to merit attention. Most writers 
have adjudged the name to the former; yet the pretensions of 
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