314 PROCEEDINGS OE THE GEOLOGICAL SOCIEIT. [May 22, 



former are serrated ; the shell, however, is proportionately much 

 longer ; from C. Ilenrici it differs in the relative proportions of all 

 its parts, being only about half the length of that shell, and is pro- 

 vided with ten whorls, while in G. Henrici there are only eight. 



Locality. In great abundance in the limestones of the zone of 

 Ammonites angidatus, Island Magee, co. Antrim. 



Turbo BrRTONi, spec. nov. 



Shell heliciform, small, as broad as high ; spire short, apex 

 obtuse, composed of 4 smooth whorls, the last inflated and rounded ; 

 aperture orbicular, umbilicus proportionately large ; columella flat- 

 tened. 



Yar. carinatus, whorls obtusely carinated. 



Locality. Marton, near Gainsborough. Collected by Mr. Waugh, 

 P.G.S. Zone oi Ammonites angulatus. 



The species is named in compliment to F. M. Burton, Esq., P.Gr.S., 

 whose collection of Lias fossils has materially increased the value of 

 the present communication. 



DisciNA HoLDENi *, spec. nov. 



Orlicula refiexa, Tate, Q. J". G. S. vol xx. p. 110 (1864). 

 Discina, sp., Terquem and Piette, Lias inf. de I'Est de la France, 

 t. xiv. f. 33, 34, p. 113 (1865). 



Shell small, regularly conical; base orbicular, the length and 

 breadth in the proportion of about 5 to 4 ; summit central ; test 

 concentrically striated. Colour black to brownish-black ; yellowish- 

 brown in the young shell. 



Dimensions of an average-sized specimen : 



millimetres. 



Long diameter 4-5 



Short diameter 3-6 



Height 2-3 



'•b^ 



This form is distinguished from the other Liassic species by its 

 regularly conical form and central apex ; and it is readily separated 

 from D. reflexa, Sow, by the latter character. 



Distribution. D. JHoldeni is somewhat common in the zone of 

 ' Ammonites angidatus " of Island Magee, co. Antrim, whence the 

 type specimens. Usually attached to Cardinia ovalis and Astarte 

 consohrina. I have collected the same species in the zone of " Am- 

 monites ibe.v/' at Cheltenham, and have seen numerous examples 

 attached to Ammonites Henlayi, probably from the zone of '^ Am. 

 capricornus," in the Collection of the Geological Survey. 



Mr. T. Davidson informs me that L. Lloldeni has been obtained 

 by Mr. J. Wilson, F.G.S., from the lower lias at Rugby. 



"'^ In compHment to my esteemed friend J. S. Ilolden, M.D., who assisted 

 me in working out the geology of the east coast of Antrim. 



