684 Geological Society. 



2. ' The Faunal and Lithological Sequence in the Carboniferous 

 Limestone (Avonian) of Burriiigton Combe, Somerset.' By Prof. 

 Sidney Hugh Eeynolds, il.A., F.G.S., and Arthur Yaughan, M.A., 

 P.Sc, F.G.S. 



Lithology. — The series is almost continuously calcareous from 

 the base of Z to D^, where the section ends ; the K beds are, to a 

 large extent, shales. Crinoids are the prevalent limestone-builders 

 throughout K, Z, and C^ ; in G^ the rock is largely of the coarsely 

 crinoidal type known as petit granit by the Belgian geologists. 



A band of coarse oolite occurs in the upper part of K^ ; but, 

 apart from this, no oolite is met with until the top of C^ is reached. 

 Cj and S^ are very largely oolitic, conspicuous white oolite pre- 

 vailing at the top of C^. There is much oolite in the upper part 

 of S,. 



An important point is the prominent part played by foraminifera, 

 which are the principal limestone-builders in C.„ Sp and much of S.,. 

 Many of the oolitic limestones are foraminif'eral ; but, especially 

 in Cg, there is much limestone abounding in foraminifera though 

 not oolitic. 



In the upper part of S^, peculiar concretionary limestones, showing 

 imperfect ' Cotham-Marble ' structure, occur; but these are not so 

 prominent as in other parts of the South-Western Province. 



The Eurrington section agrees with the other sections in the 

 South-Western Province, in showing dolomitization in the upper 

 0^ beds. A strong development of chert occurs at three levels — 

 S„ y, and Z,. 



Palaeontology. — The paloeontological portion includes notes on 

 several early mutations of well-known Carboniferous gcntes, and 

 deals, in detail, with the megastomatid Michelinias and the large 

 Caninias (C. jmtula and C. cf/lindrica). The essential similarity 

 of developmental stages in vesicular structures in widely distinct 

 groups of corals is illustrated in the cases of Caninia cylindrica and 

 Lonsdalia floriform is. 



The early Syriugothyroid stage in the Carboniferous ' Spiriferinas,' 

 a stage not observable in the Liassic type-species, is described, and 

 the generic designation of Si/nnc/othi/ris laminosa is discussed. 



A section is devoted to a comparison of the deposits at Burrington 

 Combe with those at other points of the Belgian and South-Westeni 

 Provinces. The great variability of deposit during the Mid- Avonian 

 Period is emphasized, and the rapidity of accumulation of beds of 

 crinoidal debris is compared with the slow growth of dolomitic 

 limestone at that time. 



