Length 

 Height 



mm. 

 = 12 



= 12-2 



Thickness 



= 9-3 



46 MB. A. M. DAVIES ON THE XMEEIDGE CLAY [Feb. I907, 



one differs in the umbones being less obtuse and the posterior 

 border less concave, while the form is more variable. 1 



Peotocaedia sp. 



This species occurs in a crushed and broken condition in the 

 serpulite-doggers at Brill, only one specimen being fairly perfect. 

 It differs from other Protocardiae of the same age, so far as I have 

 ascertained, by the absence of concentric striaa and the larger 

 number of the radial ribs, which are as many as 15 to 19, as against 

 the usual 8 to 10. In some specimens the first six or eight of 

 these ribs are finer than the rest ; in others they are not ; while, in 

 one case, the second and fourth alone are finer. The ribbed area 

 occupies about one-third of the length. The dimensions of the 

 most perfect specimen are : — 



mm. 



Length 

 Thickness 

 Length = *' 75 

 ? Macteomya bee vis, Agassiz. 



1842-45. Louis Agassiz, ' Etudes critiques sur les Mollusques Fossiles : Mono- 

 graphic des Myes ' p. 192 & pi. ix b, figs. 5-9. 



This species is probably the one identified in the Survey-list of 

 Arngrove fossils as ' Thracia or Anatina.' It is fairly common in 

 the Arngrove Stone, but, as it shows nothing beyond its form and 

 ornamentation, it is extremely difficult to identify. Various genera 

 of Anatinacea have species of very similar aspect, and so have 

 several genera of Tellinacea. Among the latter, Isodonta Tcimmericli- 

 ensis, Dollfus, resembles it most nearly ; but, in the Arngrove 

 specimen, the posterior area is not quite so sharply defined, and the 

 concentric striae are not so regularly spaced. The resemblance of 

 form and markings to those of Mactromya brevis is much closer. 



Seeptjla teteagoxa, J. de C. Sow. 



1829. Serpula tetragona, J. de C. Sowerby, ' Mineral Conehology ' vol. vi, p. 203 & 



pi. dxcix, figs. 1 & 2 (two varieties). 

 Non 1839. Serpula tetragona, F. A. Roerner, ' Versteinerungen des Norddeutschen 



Oolithen-Gebirges ' Suppl. p. 19 & pi. xx, fig. 17. 

 Allied species : — 

 1859. Serpula Thurmanni, Ch. Coutejean, 'Etude de l'Etage Kimmeridien dans les 



environs de Montbeliard & dans le Jura ' p. 227 & pi. xxv, figs. 13-15. 

 1873-74. Serpula Dollfussi, P. de Loriol, Mem. Soc. Phys. Hist. Nat. Geneve. 



vol. xxiii, pt. ii, p. 262 & pi. i, figs. 2 a-2 c. 



The abundant serpulae of the Brill doggers all seem to be refer- 

 able to fig. 1 of Sowerby's S. tetragona. The best-preserved 

 specimens show an ornamentation of obtusely V-shaped ridges, the 

 point directed forwards, which is not indicated by Sowerby ; but, in 

 all other respects, they agree with his figure and description. 



1 [Dr. Kitchin has kindly called my attention to another species of Ostrea, 

 nearly related to the Brill specimens. This is 0. hebridica, E. Forbes, Quart. 

 Journ. G-eol. Soc. vol. vii, 1851, p. 110 & pi. v, figs. 4a-4c. — A. M. D., 

 January 4th, 1907.] 



