76 HELICEA. 



HELIX ARIADN^E PFEIFFER. 

 PLATE LXXVIII. FIGURES 1, 3, 4. 



T. arcuato-rimata, depressa, subdiscoidea, solidula, diaphana, superne 

 plicatula, albida ; spira subplana ; anfr. 5 sutura impressa distinct!, 

 planiusculi, ultimus antice subito deflexus, valde constrictus, basi paulo 

 convexior, sublaevigatus ; rima umbilicalis areuata, in perforationem 

 obliquaua, punctiforraem terminata; apertura parvula, perobliqua, lunato- 

 circularis, ringens ; perist. breviter reflexum, marginibus conniventibus, 

 lingua bicruci, prof'unde intrante, flexuosa junctis, basali plicis 2 validis, 

 marginalibus, intrantibus, approximatis, dextro plica profunda margini 

 parallela munito. [Pfeiffer.] 



SYNONYMS AND REFERENCES. 



Helix Ariadnce PFEIFFER in Zeitsch. f. Mai. 1848, p. 120; Mon. Hel. Viv. iii. 266. 



CHEMNITZ, ed. 2, i. p. 372, pi. Ixv. figs. 19-21, (1846). 

 Helix Couchiana LEA, Proc. Phila. Acad. 1857, p. 102. 



DESCRIPTION. 



Animal not observed. 



Shell with a rounded umbilical groove, terminating in a 

 minute oblique perforation, depressed, subdiscoidal, nearly 

 transparent, bluish white, with scarcely perceptible wrinkles 

 on the upper surface ; spire flattened ; whorls five, separ- 

 ated by a distinct suture, flattened, the last one suddenly 

 falling towards the aperture, very much contracted and 

 pinched behind the peristome, more convex and smoother 

 below ; there is a deeply chiselled, rounded, umbilical 

 groove as mentioned above, the umbilical region is also 

 channelled ; aperture small, extremely complicated with 

 teeth, very oblique and circular ; peristome white, slightly 

 reflected, its terminations approaching each other and 

 joined by two flexuose, elevated, acute laminae, con- 

 verging to a point far within the aperture ; the basal por- 

 tion of the peristome is also furnished with two stout, 

 entering, converging, marginal folds, while the right ter- 

 mination of the peristome has a more delicate, deeply 

 seated, elongated lamina, running almost parallel with the 

 peristome. 



