HELIX-LUCERNA. 97 



ulate behind the aperture, descending anteriorly ; aperture very- 

 oblique, oval, with a dentiform fold inside the columellar margin ; 

 peristome white, margins joined by a callus, the upper expanded, 

 columellar margin dilated, reflexed. 



Alt. 8, diam. maj. 25, min. 22 mill. (Morelet.) 



Chocquequiras on the Apurimac river, Peru. 

 H. angrandi MOREL. Series Conchyl. iii, p. 168, t. 7, f. 3. (1863) 

 PFR., Monographia v, p. 5CK. 



Section VI. LUCERNA Swainson, 1840. 



Lucerna SWAINS. Treatise on Malacol. p. 329. Lucerna "Humph" 

 H. AND A. AD. Genera, ii, p. 198. (f Caprinus MONTF. Conch. Syst. 

 ii, p. 142.) Pleurodonta'B'ECK, MORCH, ALBERS, ALBERS-MARTENS, 

 PFEIFFER, and others, not of FISCHER DE WALDHEIM. Lyrostoma 

 MORCH, Cat. Yoldi, p. 11, not of SWAINSON. 



The name Pleurodonta was proposed for H. lychnuchus, a form 

 now classed in Dentellaria ; and if used at all, should replace the 

 latter name. Caprinus of Montf. may have been founded on H. 

 lucerna or a small form of H. acuta ; but the figure and description 

 are sufficiently vague to render any identification doubtful. 



There is a surprising amount of variation in the species of this 

 group. Specific distinctions seem to be indeed wholly artificial ; 

 and the variations in some cases connect the most dissimilar forms 

 into continuous series. Professor C. B. ADAMS, of Amherst, seems 

 to have first seen the significance of these variations, and their 

 bearing on the question of the mutability of species. (See Contribu- 

 tions to Conchology No. 10, p. 189, and in other places in the same 

 publication.) This was eight years before the publication of " The 

 Origin of Species." 



Of course the " Key ' to species given below will not always 

 enable one to name intermediate or transition forms. 



Key to species of Lucerna. 



A. SPECIES WITH NOT MORE THAN TWO TEETH ON THE PERIS- 

 TOME. 



Lip expanded all around. 



Granulate above, polished beneath ; no teeth, carmelita. 



Granulate all over ; one or two small teeth on basal lip, 



bainbridgei. 

 Outer whorl scarcely or not at all granulate, spengleriana. 



7-HELICID^. 



