194 PEOCEEDINGfS OF THE GEOLOGICAL SOCIETY. [Jan. 25, 



According to lists prepared by Mr. Etheridge for publication in 

 a forthcoming work, the British species in undoubted Rhsetic beds 

 may be summarized as follows, omitting the Sutton species. For 

 the substance of the remarks regarding affinities and distribution of 

 the species named I am also indebted to Mr. Etheridge. 



Eoraminifera, thirteen genera and twenty-seven species ; Crust- 

 acea 2, viz. Tropifer loevis from one of the bone-beds, and Estheria 

 minuta, first known in the Keuper Sandstones ; one Brachiopod, 

 Discina Townshendi, the only one known in our Rhsetic strata. Of 

 the forms named in this hst, Lima prcecursor somewhat resembles 

 L. 'punctata of the Lias ; Monotis decussata occurs at the very top of 

 the Bhaetic beds in thin limestone bands, which some writers con- 

 sider to form the bottom of the Lower Lias. Ostrea fimbriata may 

 possibly be 0. irregularis of the Lias ; but oysters are of little value 

 in such an inquiry. Pecten valoniensis, also a true Bhaetic shell, is 

 a very variable form. Plicatula interstriata probably passes into 

 the Lower Lias. Anoplophora musculoides, another true Bhgetic 

 shell, also occurs with Monotis decussata in the thin limestone bands 

 at the top, which some call Lias. Mytilus minutus occurs both in the 

 B-hsetic and Lower Lias strata. All the Gasteropoda of the Bhgetic 

 beds (not including the Sutton species) are peculiar to that forma- 

 tion ; and the same is the case with the fish. Of the Eeptilia, Plesio- 

 saurus costatus, P. Hawhinsii, and P. trie/onus are common to the 

 Bhsetic beds and the base of the Lower Lias*. The occurrence of 

 Microlestes antiquus in the Keuper Marls is an accident, its remains 

 having been washed into the strata from the neighbouring landf. Of 

 the whole, not more than four species of shells at the most pass into 

 the Lias ; and probably this may even be restricted to two. The Sau- 

 rians have a longer range ; and this is very significant. 



In this list I do not include the Sutton forms given in Mr. 

 Etheridge's list, fourteen in aU, one of which (Ostrea multicostata) is 

 also found in the Muschelkalk, and three of which (Pecten Etheridgi, 

 P. suttonensis, and Mytilus minutus) are also Lias species. Few or 

 none of the remaining forms occur associated with the shells of the 

 ordinary Ehsetic areas. The Sutton beds lie unconformably on the 

 Carboniferous Limestone, and stratigraphically and lithologicaUy are 

 inseparable from the ordinary Lias limestone. The corals, which 

 Dr. Duncan has examined, occur in small, irregular, broken layers, 

 or rather in occasional white tufaceous limestone patches, at the very 



* Since this paper was written, I have been informed by Mr. William Sanders, 

 of Bristol, that he has obtained the centrum of an Ichthyosaurus of yast size "in 

 close contact with the thick bone-bed at Aust Passage," apparently identical with 

 I. platyodon of the Lower Lias. 



t The Mendip Hills and the highlands of South Wales have been recog- 

 nized as land while the Trias was being deposited, ever since 1846, if not earlier. 

 Sir H. De la Beche (" On the formation of the Eocks of South Wales and South- 

 west of England," vol. i.p. 239 etseq^., Mem. Geol. Surv. of Great Britain) con- 

 siders the dolomitic conglomerates "on the Mendip Hills, for instance," "to 

 have been beaches among islands." See also Eamsay, ' Denudation of S. Wales,' 

 &c. p. 318. Mr. Moore also adopts the island theory, " Abnormal Secondary 

 Deposits," Quart. Joiu-n. Geol. Soc. 1867, vol. xxiii. p. 454. 



