Ch. XX.] AND ITS FOSSILS. 313 



We can scarcely avoid suspecting that the two genera above described 

 may have borne a like insignificant proportion to the entire assemblage 

 of warm-blooded quadrupeds which flourished in the islands of the 

 oolitic sea. 



Prof. Owen has remarked that, as the marsupial genera, to which the 

 Phascolotherium is most nearly allied, are now confined to New South 

 Wales and Van Dieman's Land, so also is it in the Australian seas, that 

 we find the Cestracion, a cartilaginous fish 

 which has a bony palate, allied to those called 

 Acrodus (see fig. 412, p. 321) and Strophodus, 

 so common in the oolite and lias. In the same 

 Australian seas, also, near the shore, we find 

 the living Trigonia, a genus of mollusca so fre- 

 quently met with in the Stonesfield slate. So, 

 also, the Araucarian pines are now abundant, 

 together with ferns, in Australia and its islands. Portion J f& to^S'ot Po- 

 as they were in Europe in the oolitic period. focarya magnified. (Buck- 



J i i land's Bridgw. Treat. PI. 63.) 



Endop-ens of the most perfect structure are met inferior Oolite, Charmouth, 



Dorset. 



with in oolitic rocks, as, for example, the Podo- 



carya of Buckland, a fruit allied to the Pandanus, found in the Inferior 



Oolite (see fig. 383). 



The Stonesfield slate, in its range from Oxfordshire to the northeast, is 

 represented by flaggy and fissile sandstones, as at Collyweston in North- 

 amptonshire, where, according to the researches of Messrs. Ibbetson and 

 Morris,* it contains many shells, such as Trigonia angulata, also found 

 at Stonesfield. But the Northamptonshire strata of this age assume a 

 more marine character, or appear at least to have been formed farther 

 from land. They inclose, however, some fossil ferns, such as Pecopteris 

 polypodioides, of species common to the oolites of the Yorkshire coast, 

 where rocks of this age put on all the aspect of a true coal-field ; thin 

 seams of coal having actually been worked in them for more than a 

 century. 



In the northwest of Yorkshire, the formation alluded to consists of an 

 upper and a lower carbonaceous shale, abounding in impressions of plants, 

 divided by a limestone considered by many geologists as the representa- 

 tive of the Great Oolite ; but the scarcity of marine fossils makes all com- 

 parisons with the subdivisions adopted in the south extremely difficult. 

 A rich harvest of fossil ferns has been obtained from the upper carbona- 

 ceous shales and sandstones at Gristhorpe, near Scarborough (see figs. 

 384, 385). The lower shales are well exposed in the sea-cliffs at Whitby, 

 and are chiefly characterized by ferns and cycadese. They contain, also, 

 a species of calamite, and a fossil called Equisetum columnare, which 

 maintains an upright position in sandstone strata over a wide area. 

 Shells of Estheria and Unio, collected by Mr. Bean from these Yorkshire 

 coal-bearing beds, point to the estuary or fluviatile origin of the deposit. 



* Ibbetson and Morris, Report of Brit. Ass., 1847, p. 131 ; and Morris, GeoL 

 Journ n ix p. 334. 



