HIND : THE MILLSTONE GRIT FAUNA 
27 
Localities. — The marine bed of Millstone Grit, Hazel Hill and 
Clint Quarries. The marine band associated with Glyphioceras 
spirale at Congleton Edge. 
Observations. — I figured a specimen of this species showing the 
hinge-plate and both valves, Op. supra cit., referring it to Parallel- 
odon meridionalis de Koninck, to which species it has a fairly close 
resemblance. The Belgian shell comes from the Tournasian beds 
and is less transverse, comparatively deeper and has its ornament and 
lines of growth more deeply incised and more irregular. Grammatodon 
ohtusus is comparatively deeper in a dorsoventral direction and has 
a well-marked broad byssal sinus, which is practically absent in the 
species under discussion. 
In lists of fossils from Congleton Edge I have referred to this 
species as Parallelodon obtusum. 
Several specimens have been found at each locality. 
sedgwickia transversa sp. nov. 
[Figs. 18, 19, PI. v.] 
Specific Characters. — Shell tyansversely ovate, moderately 
gibbose, compressed and narrowed posteriorly, inequilateral, somewhat 
oblique. 
The anterior end short, its margin broadly elliptical. The inferior 
border convex ; the posterior end obliquely truncate and almost 
straight, posterior superior angle obtuse. The hinge line is gently 
arcuate. The umbones are tumid, raised and incurved, placed at 
the junction of the anterior and middle thirds of the hinge plate. 
Passing backward from the umbo is a fairly well marked oblique ridge 
which marks off a very narrow dorsal slope from the rest of the valve. 
The curvature of the valve is regular but more convex from above 
downwards than antero-posteriorly. 
Interior. — Anterior and posterior adductor scars large and well- 
marked ; the former close to the margin. Hinge edentulous. 
Exterior. — The markings on the valve, as in all shells of the 
genus, consist of concentric lines of growth, strong, regular and weU- 
marked on the anterior end, and becoming finer as they cross the shell 
and gradually obsolete, so that the posterior half of the valve seems 
smooth. 
