200 RICHARDSON : THE LOWER OOLITIC ROCKS OF YORKSHIRE. 
have found their way into the collections of most geologists ^vho 
have AAorked the Oolites of the Yorkshire Coast. 
The date of the Middle Estiiarines is approximately fixed by 
the dates of the sub- and super-jacent marine beds. The Scar- 
borough Limestone being principally of blagdeni but possibly in 
part of sauzei date and the Millepore Bed of discitce it follows that 
the intervening deposits, that is, the Middle Estuarines, must be 
provisionally regarded as of witchellice-shirhiiirnice (before, 
witchellice-sonninice) hemerae. 
^LEPORE Bed. — The Millepore Bed is a well-known marine 
band in the Yorkshire Lo\A'er Oolites, but like the other marine 
bands is subject to considerable variations and ofttimes has ill- 
defined upper and lower limits — especially upper. 
Thus at Cay ton Bay, above the true Millepore-Bed is some- 
thing like 25 feet of sandstone and sandy shales which contain 
marine fossils in them, and presumably must be associated with 
the Millepore Bed. Hence, the term " Cayton Bay Beds" might 
be used for the conjoint deposit : to include (a) the overlying 
sandstones and shales with marine fossils, and (b) the Millepore 
Bed proper. In the Howardian Hills the top part of this upper 
portion (a) is sufficiently developed to have attracted special 
notice and was called the " Upper Limestone " by Hudleston. 
On the coast the Millepore Bed proper is seen best at 
Osgodby Nab at the north-eastern end of Cayton Bay, and 
at Cloughton Wyke. At Osgodby Nab the Millepore Bed, which 
is said to be about 20 feet thick here, has been broken up by the 
Avaves into huge blocks, the weathered surfaces of which exhibit 
innumerable fragments of the characteristic polyzoan Entalo- 
phora {Spiropora or Cricopora) straminm (Phil.) and of crinoids, 
etc. (Plate XXIII.). At Cloughton Wyke the MiUepore Bed 
forms a conspicuous reef and presents much the same features as 
at Osgodby Nab, only it is thinner. 
North of Cloughton Wyke the Millepore Bed becomes more 
and more attenuated and arenaceous until it is lost sight of alto- 
gether after a place " by the side of the high road from Stainton- 
dale to Bay Town [Robin Hood's Bay]." It has not been seen 
again until the whole of the moorland tract has been traversed, 
and the neighbourhood of Kirkby Knowle arrived at. Thence 
southwards it is exposed here and there on the western escarp- 
