SCALPELLUM. 37 
6. Scatpettum Hastatum. Tab. I], fig. 13. 
8. carind intra-parietibus, intra pauluhim positis, instructé ; valvd totd introrsum valde 
arcuatd, margine interno non recto; margine basali acuto, lunceolato; valvd tenu, levi, 
tecto transverse leniter arcuato; parietibus a tecto vie disjunctis. 
Carina having intra-parietes set a little inwards; whole valve much bowed inwards, 
with the inner margin not straight; basal margin sharply pointed, spear-shaped; valve 
thin, smooth; tectum: in a transverse line flatly arched; parietes barely separated from 
tectum. 
Grey Chalk, Dover, Mus. Brit. 
Carina smooth, narrow, furnished with intra-parietes, widening gradually from the apex 
downwards ; extremely much arcuated, so that the uppermost part, of which none, or very 
little, projected freely, is at ght angles to the basal part. Not only is the dorsal surface 
considerably arcuated, but so are the inner margins, which is much more important. Basal 
margin sharply pointed, with the two edges meeting each other at about an angle of 75°. 
Roof with the two sides continuously and flatly arched; parietes rather narrow, slightly 
concave, barely separated from the tecta: the concavity of the parietes, as seen on the basal 
margin, together with the sharpness of the central portion, makes the lower part of the 
valve spear-shaped. ‘The intra-parietes are set a little within the parietes; they extend 
down to about two thirds of the entire length of the carina, and not to the basal margin of 
the parietes: they are widest at about only one fourth of the entire length of the carina 
from the apex, and here they equal in width the rest of the valve. Internally the valve 
is, in the upper part, owimg to the wide intra-parietes, deeply concave; in the lower part, 
only slightly so. 
Length of carma, measured along the chord of the arch, ‘75 of an inch. 
Afinities. This species certainly comes very near to S. mavimum; but I think it is 
distinct, and is its representative in the Grey Chalk. I have seen only a single specimen. 
The carina differs from the former varieties and species in its smoothness, thinness, in 
the acumination of the basal margin, in its much arcuated form, and more especially (for 
this, probably, would greatly influence the outline of the terga,) in the inner margins being 
also thus arcuated. 
7. ScALPELLUM aNeustum. Tab. I, fig. 2. 
XIPHIDIUM ANGusTUM. Dixon. Geology of Suffolk, tab. xxviii, fig. 9. 
S. caring angusta, introrsum valde arcuatd; tecto a parietibus rectangulé inflexis costd, 
(wt videtur) chisjuncto ; intra-parietibus usque ad dimidium valve pertinentibus, deinde 
oblique et abrupte truncatis ; margine basali acute cuspidato. 
