28 HIND : THE MILLSTONE GRIT FAUNA 
Dimensions. — Fif^. 18, PI. V., measures: — 
Anteroposteriorly, 50 mm. 
Dorsoventrally, 35 mm. 
From side to side, 22 mm. 
Locality. — Millstone Grit, Hazel Hill near Ripon and boulder 
near Masham. 
Observations. — Two specimens of this species have been obtained. 
Each is a cast of the interior of both valves. The figured specimen 
was in a matrix which showed the characteristic external ornament of 
the genus. 
Sedgivickia transversa is comparatively much less deep dorso- 
ventrally than aS. gigantia, and more tumid. 
It is not likely to be mistaken for any other species of the genus. 
sanguinolites modiolaris, sp. nov. 
[Fig. 23, PI. v.] 
Specific Characters. — Shell transverse, very inequilateral, 
modioliform. The anterior end is very short and narrowed, its margin 
rounded. The inferior border is straight, the posterior bluntly rounded 
and the hinge line straight, gently raised as it passes backwards. The 
umbones are placed very far forward, not terminal, narrowed and 
compressed, only slightly raised. Projecting backwards from the umbo 
is a well marked ridge which is separated from the rolled external 
margin of the escutcheon by a elongate concavity, which becomes 
slightly broader and shallower as it approaches the posterior superior 
angle. Below this ridge is the dorsal slope, which passes almost 
imperceptibly into the rest of the valve, but in some and more adult 
specimens there is a tendency to form an obscure oblique ridge from 
the umbo to the posterior inferior angle. The tumid portion of the 
valves is oblique from the umbo to the posterior inferior angle, in front 
of and below which the valve is gently compressed. The escutcheon 
is well developed. On the dorsal slope another obscure radiating line 
is sometimes seen. 
Interior. — The large, marginal, deep, anterior muscle scar, with 
the ridge behind it, so typical of the genus, is well marked. Hinge plate 
apparently edentulous and normal. 
