214 PARIS : NOTES ON SOME YORKSHIRE ECHINOIDS. 
Pygaster semisulcatus which has been examined from Yorkshire, 
the aperture was not displayed, and as the size of the aperture 
is the main feature that distinguishes this species from Pygaster 
macrostoma Wright, it was not possible to make an exact specific 
determination. It might perhaps be an intermediate form be- 
tween P. semisulcatus and P. macrostoma, since the latter occurs 
at a much higher horizon than the former, namely in deposits 
of schlcenbachi date. Both Trochoiiara depressum and Cidaris 
bouchardi are persistent species and range from the bottom to the 
top of the Inferior Oolite in the West of England. 
II. NOTES ON THE SPECIMENS EXAMINED. 
ACROSALENIA LYCETTI Wright. 
Two examples of this species from the Dogger of Glaisdale, 
near Whitby, have been examined. In the West of England 
this echinoid attains its maximum development in deposits of 
murchisonoe date, though it has also been found in deposits of 
hradfordensis hemera.^ 
Cidaris bouchardi Wright. 
The interambulacral plates of a Cidaria which occurs 
frequently in the Millepore-Bed agree precisely with those of 
C. bouchardi from the Inferior Oolite of the Cheltenham area. 
Unfortunately, the ambulacra are not preserved in any of the 
specimens I have examined from Yorkshire. 
Localities : — Cloughton and Ewe Xab. 
? Cidaris sp. 
A badly preserved portion of an ambulacrum from the Yellow- 
Beds at the Peak. 
Polycyphus deslongchampsi Wright. 
This species appears to be fairly common in the Dogger at 
Glaisdale, near Whitby. 
Trochotiara depressum (Agassiz). 
As in the Cotteswold district this species has a considerable 
range, occurring both in the Millepore-Bed and in the Scarborough 
Limestone. The specimens from the Millepore-Bed are usually 
very small. 
1 Proc. Cotteswokl Nat. F.C., Vol. XVI. pt. 2 (1908), p. 164. 
