242 LTTTORINIDiE. 



Tectarius, Yalencieunes. 



Syn. — Moiiodonta (partim), Lam. Pagodus, Gray. Pago- 

 della, Swains. 



Distr. — Tropical. World-wide. T.pyramidalis^ Quoy (Ixix, 24). 



Shell conical ovate or turbinated, surface tubercular or muri- 

 cated, frequently angulated or biangulated on the middle of the 

 last whorl ; aperture striated within ; axis usually imperforate. 

 Operculum paucispiral, with a broad membranous border. 



ECHiNELLA, Swaius. (Nina, Gray.) Depressed trochiform, 

 more or less distinctly umbilicated. Operculum multispiral. 

 T. Gumingii, Phil. (Ixix, 25 \ 



EUCYCLUS, Deslongchamps. (Amberleya, Morris and Lycett.) 

 Shell very thin, spire elongated, almost turriculated ; lip serai- 

 circular, thin ; columella flattened ; imperforate. 23 sp. Jurassic, 

 Liassic ; Europe. E. oheliscus, Desl. Amberleya has priority 

 but is insufficiently characterized. 



BRACHYTREMA, Morris and Lycett. Shell small, turreted, 

 turbinated ; whorls either costated, nodulated, or cancellated ; 

 the last whorl large and ventricose ; columella smooth, rounded, 

 twisted near its base, and reflected outwards, forming a short, 

 oblique canal ; aperture moderateh^ subovate, its length being 

 usually less than that of the spire. Some species, as B. varicosa 

 and B. pygmsea, acquired at certain arrests of growth thickened 

 outer lips or varices, as in Triton. 16 sp. Lias ; Europe. This 

 form has been referred to the Cerithiidae, but its shape, aperture 

 and sculpture all remind one of Tectarius; indeed, I doubt if it 

 be really distinct from Eucyclus. 



Modulus, Gray. 



Distr. — 10 sp. W. Indies, W. tropical America, Philippines. 

 M. tectum^ Gmel. (Ixix, 2'!). 



Shell top-shaped, spire depressed, ribbed or tubercular, rather 

 thin ; narrowly umbilicated ; columella with an anterior curA^ ed 

 tooth. Operculum spiral. 



Animal with eyes on the middle of the tentacles. 



RiSELLA, Gray. 



Distr. — 10 sp. Australia. R. melanostoma^ Gmel. (Ixix, 28). 



Shell depressed trochiform, with flattened whorls and keeled 

 periphery ; not umbilicated ; aperture rhomboidal, marked with 

 brown inside the margin. Operculum paucispiral. 



These shells are distinguished from Trochus, which they 

 resemble in form and sculpture, bj^ their non-nacreous interior ; 

 the animal by eyes on the tentacles instead of on peduncles, and 

 by the absence of the lateral membranes of the foot. 



PLESIOTROCHUS, Fischer. Shell imperforate; conic-elongate, not 

 varicose ; whorls numerous ; aperture subrhomboidal, smooth 



