Vol. 63.~] AND COEALLIAN ROCKS OP BRILL. 47 



Reamer's species is differently shaped in transverse section, being- 

 trapezoidal instead of square, the attached face being the broadest 

 and the upper face narrow and distinctly concave. 



S. Thurmanni, Contej., differs in the more strongly-carinate 

 edges, smoother surface, and slightly-smaller size (diameter 1*5 mm. 

 instead of 2 mm.). S. Dollfussi, de Lor., is decidedly smaller 

 (diameter 1 mm.) and straighter than S. tetragona. It may be 

 doubted whether these two forms should be regarded as distinct 

 species, or whether they should not rather be considered as varieties 

 of S. tetragona. 



Serpula. convoltjta, Goldfuss. 



1826-33. Serpula convoluta, Goldfuss, ' Petrefacta Germanise' p. 228 & pi. lxvii, 



fig. 14. 

 Non 1826-33. Serpula convoluta, Minister, Goldfuss, op. cit. p. 232 & pi. lxviii, 



fig. 17. 



This species does not appear in the lists of Jurassic fossils in the 

 Geological-Survey Memoir on the Jurassic Rocks of Britain. It is, 

 therefore, probably new to Britain. 



Five specimens were found, four of which were dextral and one 

 sinistral. They agree closely with Goldfuss 's figures, which include 

 both dextral and sinistral forms. 



Although Goldfuss's own species and Miinster's (both Jurassic) 

 are described and figured very near together in the same book, 

 under the same name, Bronn's ' Index Palaeontologicus ' (p. 1136) 

 gives priority to Goldfuss's name. Bronn, however, identifies the 

 species with Vermicularia nodus, Phillips. 1 The rather unsatis- 

 factory figure given by Phillips makes this identification possible, 

 but V. nodus has been subsequently figured more carefully by 

 Morris & Lycett, 2 and it is certainly not the same as Goldfuss's 

 species. The name Serpula convoluta. Goldfuss, should therefore 

 stand. 



Occurrence. — Zone of Eocogyra virgula, Brill Brick & Tile 

 Company's brickfield, at the foot of Rid's Hill, Brill (Bucks). 



[Specimens of Cyprina cyreniformis (?), Ostrea cf. dubiensis, and 

 Serpula convoluta, from Brill, have been presented to the Museum 

 of Practical Geology, Jermvn Street. — A. M. J)., January J$i, 

 1907.-] 



EXPLANATION OF PLATE I. 



Fig. 1. Thin transverse section of Belemnites abbreviates, Miller, Lower 

 Kirneridge Clay, Brill ; showing the partial replacement of calcite 

 by selenite. X 15. The unaltered calcite can be distinguished by 

 the cleavage-cracks (see p. 33). Original in Dr. Cullis's Collection. 



2. Thin section of Arngrove Stone (Ehaxella-Ghevt), Arngrove, Boar- 



stall (Buckinghamshire). X 40. The two varieties of spicules can 

 easily be distinguished (see p. 38). 



3. Thin section of the calcareous variety of Arngrove Stone, Warren 



Farm, Studley (Oxfordshire). X 40. (See p. 39.) 



i ' 



Geology of Yorkshire' 1829, p. 152 & pi. ix, fig. 34. 



2 'Great Oolite Mollusca' Monogr. Palreont. Soc. pt. i (1850; p. 120 & 

 pi. xiv, figs. 8 a-S b. 



