CYLICHNA. 289 



Subdivisions of Cylichna. 



Subgenus Cylichna Loven. 



Shell subcylindrical, the apex either concealed or umbilicated ; 

 surface unicolored whitish or brownish ; columella with one indis- 

 tinct fold or none. A further division of this subgenus will eventu- 

 ally be made, but in the present state of our knowledge of the group, 

 the natural sections of Cylichna cannot be defined. 



Subgenus Mnestia H. & A. Adams. 



Shell ovate-cylindrical, marbled or banded. Spire innuersed in 

 the deep umbilicus. Anatomy unknown. 



Subgenus Cylichnella Gabb. 



Shell oblong-oval ; spire concealed, imperforate ; columella with 

 a callous fold, and below it a nodule-like fold. Anatomy unknown. 



Subgenus Cylichna Loven. 

 Species of the North Atlantic, Arctic and Mediterranean Seas. 



C. CYLiNDRACEA Pennant. PI. 29, figs. 15, 16, 17. 



Shell cylindrical with parallel sides slightly tapering toward each 

 end, squarely truncated above; solid and opaque. Surface slightly 

 glossy, covered with a brownish-yellow cuticle ; sculptured with 

 numerous fine, superficial spiral stride. Apex appearing like a 

 slightly concave disc bounded by an angular keel, the whorls not 

 visible. Aperture as long as the shell, narrow and parallel-sided 

 above, suddenly expanding at the base. Lip strongly retracted 

 above, forming a large, deep sinus ; straight in the middle, and 

 again retracted and eftuse at base. Columella thickened, with a 

 broad but indistinct fold. Alt. 11, diara. 2:1 mill. 



European seas from Norway to the Canaries and Azores ; Mediter- 

 ranean; Whydah, W. Africa; St. Helena (Smith); Ascension I., 

 420 fms. ayid Tristan da Cunha (Challenger). 



Bidla cylindracea Pennant, Brit. Zool. iv, p. 117, pi, 70, f. 85, 

 1777. — Cylichna. cylindracea Loven, Ind. Moll. Scand. p. 142, 1846. 

 — Jeffreys, Brit. Conch, iv, p. 415 ; v, pL 93, f. 4-5. — Saks, Moll. 



