26 
HIND : THE MILLSTONE GRIT FAUNA 
Cayton Gill Beds, and may be said to have a Pendleside facies. If 
this bed is shown to be below the Cayton Gill Beds, then we at once 
have evidence of the fact that at the close of the Dibunophyllum 
period in the area in discussion, the fauna was not extinguished, but 
merely migrated and returned at a much later date when the con- 
ditions were favourable, but though favourable very different from 
those of the Carboniferous Limestone sea. 
In connection with this band the occurrence of Prothyris elegans 
is interesting This shell occurs in the Millstone Grit of Scotland, 
and I have obtained it from Congleton Edge quarry just above the 
zone of Glyphioceras spirale. It is a North American species and is 
not uncommon in the Coal Measures of Nebraska. 
GRAMMATODON REGULARIS Sp. nOV. 
[Figs. 12-14 ; Plate IV.]. 
Parallelodon meridionalis Hind, 1897. Brit. Carb. Lamell., PI. XIII., 
Fig. 9. 
obtusum, 1902, Trans. N. Staff. F. C, Vol. XXXVI., 
Page 78. 
Specific Characters. — Shell transverse, narrow and tumid, 
very inequilateral. The anterior border rounded. The lower border 
and hinge line almost parallel, the posterior border obliquely truncate 
from above downwards and backwards. The posterior superior 
angle obtuse. Umbones small, somewhat raised, nearer the anterior 
end. The valve is moderately tumid except on the dorsal slope where 
it is rapidly compressed and hollowed above an oblique rounded 
ridge passing from the umbo towards the posterior inferior angle. 
Escutcheon large and well marked. 
Interior. — The hinge plate and muscle scars normal. 
Exterior. — The surface is ornamented with fine lines of growth 
which become more pronounced and thicker on the posterior part of 
the valve. Fine decussating radiating lines are to be noted, which 
become much more apparent on the dorsal slope. 
Dimensions. — Fig. 14, PL IV. measures : — 
Anteroposteriorly, 32 mm. 
Dorsoventrally, 11 mm. 
Transversely, 10 mm. 
