ON SOME FOSSILS FROM THE INFERIOR OOLITE. 48' 



28. Notes on some Fossils, chiefly Mollusca, from the Inferior 

 Oolite. By Rev. G. F. Whidborse, M.A., F.G.S. (Read 

 March 7, 1883.) 



[Plates XV.-XIX..] 



In surveying the Inferior Oolite as it appears in the West of Eng- 

 land generally, the conditions of deposition seem to differ from 

 those of the Great Oolite as displayed at Minchinhampton, where, 

 in the great frequency of rolled and broken organisms and the ex- 

 treme false bedding, we have indications of a shore-deposit formed 

 by a roughish sea. The fossils of the Inferior Oolite, on the other 

 hand, are usually better preserved and unbroken ; they are often 

 crowded, and lie one inside another, but rarely show great signs of 

 being rolled ; so that they do not seem to have been much exposed 

 to actual breakers. At the same time the strata would appear to 

 have been often laid down in shallow water ; such shells as oysters, 

 pectens, and astartes are frequent ; the univalves are often spinose 

 and nodular; signs of vivid colouring occasionally remain ; corals 

 and sponges commonly occur ; and the shell-structure of many species 

 is massive, owing to their not being deep-sea forms. 



It is interesting to notice the great definitiveness with which beds of 

 different shells succeed each other. For instance in the iron-shot beds 

 of Dundry there is hardly a sign of a Terebraiula or of the common 

 form Pholadomya Heraulti, while in adjacent beds these two fossils 

 occur in crowds; a little higher up corals are common, while the mol- 

 lusca are, to a great degree, absent. In the same way in Dorsetshire 

 beds appear very full of sponges, though these are very rare in other 

 parts of the formation ; nor is it less striking to observe the thick 

 beds of sand which are locally interposed at various horizons. We 

 may therefore believe that the deposits were formed at an irregu- 

 larly varying level, but in shallow water, and probably not near the 

 entrance of any river. 



The absence of the vertebrata is marked ; but a Strophodus 

 occurs at Broadwindsor, and an Oxyrhinal at Dundry. Acrodus 

 is quoted by Phillips, in his 4 Valley of the Thames,' from near 

 Stroud, and teeth and palates by Wright in the Quart. Journ. Geol. 

 Soc. vol.xvi.p. 40, from Ravensgate Hill. I am not aware of any other 

 species till we come to the rich Sevenhampton and Stonesfield beds, 

 with their vertebrata and even mammals. 



The large size of the mollusca, especially Pelecypoda or bivalves, the 

 great number and variety of gigantic Cephalopoda, and the presence 

 of numerous fine species of corals and Echini would point to a tem- 

 perature considerably warmer than at present. On the whole, the 

 fossils would appear to increase in size and variety as we go south- 

 wards. This is less seen in the Lamellibranchs and Brachiopoda 

 than in the Cephalopoda and Gasteropoda. These latter are rare in 

 the Cotteswold and Midland districts, common at Dundry, and abun- 



Q.J.G.S. No. 156. 2n 



