242 LITTORINID &. 
Trecrarius, Valenciennes. 
Syn.—Monodonta (partim), Lam. Pagodus, Gray. Pago- 
della, Swains. 
Distr.—Tropical. World-wide. 7. pyramidalis, Quoy (1xix, 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, Swains. (Nina, Gray.) Depressed trochiform, 
more or less distinctly umbilicated. Operculum multispiral. 
T. Cumingit, Phil. (Ixix, 25). 
EucYCLUS, Deslongchamps. (Amberleya, Morris and Lycett.) 
Shell very thin, spire elongated, almost turriculated ; lip semi- 
circular, thin ; columella flattened ; imperforate. 23sp. Jurassic, 
Liassic; Europe. #. obeliscus, 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 moderately subovate, its leneth being 
usually less than that of the spire. Some species, as B. varicosa 
and B. pygmea, acquired at certain arrests of growth thickened 
outer lips or varices, as in Triton. 16sp. Lias; Europe. This 
form has been referred to the Cerithiidz, but its shape, aperture 
and sculpture all remind.one of Tectarius; indeed, I doubt if it 
be really distinct from Eucyclus. 
Moputus, Gray. 
Distr.—10 sp. W. Indies, W. tropical America, Philippines. 
M. tectum, Gmel. (1xix, 27). 
Shell top-shaped, spire depressed, ribbed or tubercular, rather 
thin; narrowly umbilicated ; columella with an anterior curved 
tooth. Operculum spiral. 
Animal with eyes on the middle of the tentacles. 
RIseELLA, Gray. 
Distr.—10 sp. Australia. R. melanostoma, Gmel. (1xix, 28). 
Shell depressed trochiform, with flattened whorls and keeled 
periphery ; not umbilicated ; aperture rhomboidal, marked with 
brown inside the margin. Oper culum paucispiral. 
These shells are distinguished from Trochus, which they 
resemble in form and sculpture, by 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 
