HELIX-LABYRINTHUS. 1 59 



H. vexans DOHRN, Nachrichtsbl. d. Mai. Gesell., vii, 1875, p. 57 ; 

 Jahrbiicher d. Malak. Gesell., 1875, p. 294, 1. 10, f. 3, 4 ; Continuation 

 of Conchy 1. Cab., p. 626, t. 180, f. 3, 4. PFR., Monograpbia Hel. 

 Viv., vii, p. 591. 



Separated from H. aenigma by tbe lack of granulation, almost 

 horizontal aperture, and the last whorl is not keeled. 



Section X. LABYRINTHUS Beck, 1837. 



Labyrinthus BECK, Index Molluscorum, etc., p. 33 (Type, " L. 

 otis"=H. labyrinthus Desh.). ALBERS, Die Heliceen, p. 121, 1850. 

 ALBERS-MARTENS, Die Heliceen, ed. 2, p. 154 (1860). H. & A. 

 ADAMS, Genera Rec. Moll., ii, p. 200 (subg. ofLucerna). KOBELT, 

 111. Conchylienbuch, p. 226 (sect. Lucerna). PFEIFFER-CLESSIN, 

 Nomenclator Heliceorum Yiventium, p. 174. 



Labyrinthus occupies those parts of Northern South America not 

 inhabited by species of Isomeria, and generally less elevated country 

 than the mountainous Andean region to which the latter group is 

 confined. 



The two groups have much in common ; but while in Isomeria 

 the teeth are much reduced, sometimes absent or minute, in 

 Labyrinthus they are more developed than we find them in any other 

 group of Helices. The lower country of Northern South and 

 Central America will probably be found to be inhabited by some 

 group of snail-eating Carabidse not found in the Andean region 

 where Isomeria lives ; and the elaborate labyrinthine lip-armature of 

 Labyrinthus has been evolved to protect these snails against their 

 coleopterous enemies. 



In Labyrinthus there are three primary folds or teeth : the parietal, 

 an erect entering or oblique lamina, the outer basal, usually flattened, 

 compressed, or bifid, and the inner basal. These three are present 

 in every known species. As secondary folds may be classed the 

 superior lip-tooth (of H. bogotensis, otostoma, leucodon, etc.), a 

 conical process, never very large, developed on the inner edge of the 

 upper portion of the lip, the accessory columellar tooth, formed by 

 the division of the inner basal tooth (seen in H. dunked, bogotensis), 

 and the superior palatal fold, a minute, acute fold developed on the 

 upper wall well within the aperture, in H. labyrinthus, plicata, etc. 

 This last is rather inconstant in the species possessing it. 



The shell of Labyrinthus is not oblong nor transversely dilated, as 

 Isomeria usually is ; it is not malleated ; the surface is microscopically 



