146 MOLLUSCA. 
last whorl, this may be compared with C. columna, Sowb., but it 
differs entirely in sculpture; its beak is very much shorter, and it is 
very much smaller. 
CERITHIUM INVAGINATUM (Gould). 
Testa elongato-turrita, sordidé alba, ad apicem et interdum ad rostrum 
rufescens, filis tenuibus cincta: spira anfractibus decem ad duodecim 
angulato-convexis, superné tabulatis, inferné constrictis, nodoso-plicatis 
et concinné lamelloso-rugosis, ultimo carinato: apertura subquadrata, 
alba ; rostro gracilt, recurvato. 
Cerithium invaginatum, Goutp ; Proceed. Boston Soc. Nat. Hist.. 
in. 120. May 1849. Expedition Shells, 61. 
SHELL turreted, of a dead, dingy white colour, dusky brown at tip 
and usually at the beak, girded with several fine, unequal, raised 
threads; whorls ten to twelve, angularly convex, bearing about eight 
tubercular folds, shouldered posteriorly, and most delicately barred 
with lamellar wrinkles; anteriorly deeply girt in, and channeled at 
the suture; the basal whorl has also a keel-like ridge, revolving just 
behind the beak, giving the whorl a triangular outline. Aperture ren- 
dered somewhat quadrangular by the termination of the ridge; poste- 
rior canal quite closed in; columella moderately arcuated and slightly 
clothed with callus; canal long and delicate, recurved and inclined to 
the left. 
Length seven-eighths of an inch; breadth one-fourth of an inch. 
Inhabits the Feejee Islands. 
This is a very peculiar species, quite different from any hitherto 
described. The tuberose whorls, rendered unusually independent 
by the deep constriction at the suture, causing them to appear, when 
viewed from above, as if thrust into each other, and the very delicate 
wrinkling of their superior portion renders the diagnosis clear. 
Figures 169, 169 a, two views of the shell; 169, details of sculp- 
ture. 
