1865.] DUNCAN SUTTON-STONE COKALS. 91 



them in South Wales adds to the probability of their having a greater 

 vertical range than has hitherto been supposed, from their fol- 

 lowing the lavf^ that the widely wandering in space are persistent in 

 time. 



There are some considerations respecting the range of some Rhaetic 

 and Liassic moUusca, both in England, Prance, and Switerland, and 

 concerning the alternations of the Avicula-contorta and Dachstein- 

 bivalve and the coralliferous strata in the Kossen and Dachstein di- 

 visions of the Alpine Trias, which strengthen the necessity for caution 

 in correlating distant Triassic strata possessing species in common. 



Moreover it cannot be admitted that the coral fauna of the period 

 is fairly represented in the Alpine Trias, great as its number of 

 genera may be. It is also remarkable that the Avicula-contorta 

 series should be very uncoralliferous : doubtless the Aviculce with 

 their associated bivalves and generally puny Gasteropods were 

 dwellers in a muddy area, where only stunted and simple Madrepo- 

 raria can live. 



The alternations of the strata just mentioned, and the great vertical 

 range of some species, indicate that although the succession of the 

 Upper Triassic, Rhaetic, and Lower Liassic strata is to be traced in 

 ascending order, still this succession may have a very doubtful chro- 

 nological meaning. The species which form the little coral fauna of 

 the Sutton series do not indicate a vigorous condition of the polype- 

 life of the period : their affinity with the Alpine St, Cassian species 

 is beyond doubt ; and whatever their age may be, they are still the 

 oldest amongst- the Mesozoic forms in this country. 



This is a conclusion which was determined irrespectively of Mr. 

 Tawney's researches, and it is strengthened by them. The absence 

 of the usual species of the mollusca of the Avicula-contorta beds, the 

 close proximity of these beds, the existence of a number of local spe- 

 cies, and the localization of the Sutton Stone in the west indicate 

 that the series resting on the Mountain-limestone is older than the 

 " con^or^a" -bearing strata. How much older, is of course subject to 

 the application of the remarks already made. 



List of the Species. 



4. Astrocoenia Oppeli, Laube, 3 vars. 

 6. Montlivaltia, sp. 



L Rhabdophyllia recondita, Laube. 



2. Thecosmilia rugosa, Laube. 



3. Elyastr£ea Fischeri, Laube. 



'HemarJcs on the species. — The three species at the head of the list 

 are described and admirably delineated iuGustavLaube'swork. Bhah- 

 dophyUia is a well-known Jurassic genus, and was doubtless one of 

 those misnamed Lithodendron in the Alpine Trias. The species recoti-- 

 dita is a very well-marked one, and the singular disposition of the 

 smaller septa to bend towards the larger is very distinctive. The 

 genus is unknown in the British Lias, and the species is only re- 

 motely related to the Oolitic forms. 



The Thecosmilia rugosa is a compound coral, stunted in growth, 

 and given to fissiparous division of its calicos ; the rugose transverse 

 markings of the epitheca are well shown, both in Laube's drawing 



