TURRITELLA. 195 



Genus MATHILDA, Semper, 1865. 



Shell turriculated, rather solid, apex heterostrophe, abruptly 

 turned from left to right ; whorls in the typical species trans- 

 versely cingulated and reticulated, longitudinally striated ; aper- 

 ture entire, subrotund, base sometimes subeffuse ; lip acute, 

 columella smooth. Operculum corneous, rather solid, multi- 

 spiral, the external face concave, nucleus central. 



Animal with very long thread-like, divergent tentacles, with 

 rather large eyes on prominences upon their exterior side, about 

 a quarter of their length from the base ; foot large, cut out in 

 front, obtuse behind ; operculigerous lobe having a row of cilia 

 in constant movement. 



Seas of Europe, China, Australia, Strait of Magellan. 



There are about thirty tertiary and a few secondary species. 



" Mathilda," writes Dr. Fischer, " has the shell of Turritella, 

 with the heterostrophe embryonic whorls of Pyramidella ; the 

 exterior form of the animal, the position of the eyes, and the 

 structure of the operculum, relate it to the former." On the 

 other hand, Monterosato finds in it affinities with Solarium, and 

 Jeffreys places it in the Pyramidellidse. The radula is unfortu- 

 nately unknown. 



Subgenus GEGANIA, Jeffreys, 1884. 



Shell small, conic, reticulated, imperforate, the nucleus glob- 

 ular and twisted, not spiral and not sinistral. G. PINGUIS, Jeffr. 



Coast of Portugal (abyssal). 



Differs from Mathilda in its short spire and non- heterostrophe 

 apex. 



Genus TURRITELLA, Lam., 1799. 



Section TURRITELLA (typical). 

 T. TEREBRA, Linn. PL 59, figs. 32, 33. 



Whorls convex, each with about 6 revolving ridges and inter- 

 mediate close strise, suture deep ; yellowish brown to chestnut- 

 color. Length, 5-8 inches. 



Singapore, Java, Philippines. 



T.*Archimedis, Dillwyn, is a synonym, and T. spectrum, Reeve 

 (tig. 33), is at most a variety, developing more numerous ridges. 



