146 ORGANIC REMAINS. 



it certainly demands a caution in their application, which is not always 

 observed. 



Several fossils not peculiar to the cornbrash, as, millepora straminea, 

 pinna cuneata, amphidesma securiforme, and a. decurtatum, unio pere- 

 grinus, vermicularia nodus, and ostrea Marshii, seem to be repeated only 

 in the lower oolitic formation, and the large variety ? of modiola cuneata, 

 melania vittata, and perhaps pecten demissus, have yet been found only 

 in the upper oolite formation ; whilst the remains of echinida and pen- 

 tacrinus, mya literata, sanguinolaria undulata, trigonia clavellata, pecten 

 fibrosus, trochus granulatus, terebra granulata, and melania Hedding- 

 tonensis, are common to both these formations, either in Yorkshire 

 or in other parts of England. The cornbrash is the only conchiferous 

 stratum in the eastern part of Yorkshire from which belemnites are 

 excluded, and it seems at present to be the only repository of clypeus 

 orbicularis, isocardia minima, cardium citrino'ideum, plagiostoma rigi- 

 dulum, terebratula ovoides, and t. digona, ammonites Herveyi, and 

 a. terebratus. But though these shells should eventually be discovered 

 in other strata, the cornbrash may still be discriminated in any local dis- 

 trict, and satisfactorily identified in distant countries. By its clypei, 

 galerites, and cidarites, geologists will at once refer it to the strata 

 which intervene between the Kimmeridge clay and the lias ; the 

 abundance of amphidesma securiforme, isocardia minima, pinna cuneata. 

 and ostrea Marshii, and the absence of gryphasa dilatata, ammonites 

 perarmatus, and spatangus ovalis, will connect it with the Bath oolite 

 formation generally, whilst a faithful comparison of its whole suite of 

 organic remains, with those of the Stonesfield slate and forest marble, 

 and upper arid lower oolites of Bath respectively, will always be sufficient 

 to discriminate these rocks, even where no aid can be derived from ob- 

 servations of its geological position. The specimens which I have had 

 the opportunity of consulting, are insufficient to demonstrate the ex- 

 istence of cornbrash in a distinct character above the coal of Brora. 



