432 



The lower part of this bed is characterized by the presence oiPerna 

 quadrata, and the upper by numerous remains of the following shells : 



Melania Heddingionensis, Ammonites Blugdeni, Terehratida spinosa, Gry- 

 phcBa nana, Ostrea Marshii, Pecten lens, Plagiostoma interstinctiim (c), Avi- 

 cula Braamburiensis (c), A. ecltinata{c) ? Gervilia acuta (c), Trigonia cos- 

 tata, T. daveUata, Astarte minima (c), Corbula deprcssa, Pinna cuneata, 

 Pentacrinites vulgaris, Cidaris vagans. 



The author then describes the upper beds of the Great Oolite at 

 the two extremities of Cayton Bay, and at low water at the south 

 side of Carnelian Bay. 



Top. Irony nodules, without organic remains 1 ft. 



Extremely hard ironshot rock, composed almost wholly 

 of fragments of fossils, viz. Millepora straminea, pa- 

 pillce of a Cidaris, innumerable small spines, probably 

 of Cidaris vagans, muricated spines, and joints of a 

 Pentacrinites S ft. 



This bed Mr. Williamson appears to consider peculiar to the lo- 

 calities mentioned, not having observed it elsewhere. 



He afterwards describes the upper beds of the Great Oolite at the 

 south point of Cayton Bay. Immediately above the nodular iron- 

 stone bed is a very thick series of sandstones and shales surmounted 

 by a seam of argillaceous oolite, containing Avlcula Braamburiensis, 

 and similar to that which forms the top of the Great oolite at White 

 Nab (No. 6. of the section), with the exception that the nodular iron- 

 stone is wanting. This system of sandstone and shale, considered 

 by Mr. Phillips to belong to the upper marl and sandstone, is, in Mr. 

 Williamson's opinion, a distinct and merely local deposit included 

 in the superior division of the Great oolite. It contains most of the 

 fossil plants assigned by Mr. Phillips to the upper marl and sandstone, 

 and several which are new and peculiar to it. An ascending sectional 

 list is given of this deposit, commencing with the 1 foot bed of irony 

 nodules, and passing through 35 feet of alternations of shale, with 

 ferruginous and other sandstones, ends in the seam of argillaceous 

 oolite, which is said to be overlaid by the upper sandstones and shales. 

 One of the beds of shale contains a vast number of plants, amounting 

 to above 40 species. The following list is given by Mr. Williamson : 



Pecopteris lobifolia, P. insignis, P. undans, P . polypodioides, P.propingua, 

 P. Williamsonis, P. acutifolia, P. obtusifolia, P. dentata, P. exilis, P. c<s- 

 spitosa, Neuropteris recentior, N. ligata, N. arguta, Sphenopteris stipaia, 

 S. Williamsonis, Cyclopteris digitaia, Glossopteris Phillipsii, Taniopteris 

 vittata, T. major, Solenites Murrayana, Lycopodites Williamsonis, SjiheEridia 

 paradoxa, Pterophyllum comptum, P. Pecten, P. minus, Otopteris cuneata, 

 0. Beanii, Ctenis falcata, Dictyophyllum rugosum, Cycadites tenuicaulis. 



Two shells are occasionally found in these beds, and are considered 

 by the author to be allied to the genus Anodon. 



In conclusion, Mr. Williamson says, that the characteristic shells 

 of the Great oolite are hw, as they bear a general resemblance to 

 those of the cornbrash and inferior oolite. 



(c) The species thus distinguished are found in the greatest abundance. 



