Highest Coal-measures of Durham. 207 



was bivalvular and cannot be either an Ancyhis or a Discina. It 

 seems unfortunate, however, that a shell from the Upper Coal- 

 measures of the North Staffordshire Coalfield, which from the 

 illustration and description seems beyond doubt to be a true and 

 adult form of Carbonicola, should have had the specific name of 

 " Vinti" attached to it on the assumption that it is identical with 

 the chitinous organism from Claxheugh. 



The name has now found its way into Continental publications. 

 E. Haug, 1 speaking of the Coal-measures of Great Britain, says: 

 "The Upper series is characterized by intercalations of beds of 

 Anthracomya Phillipsi and Carbonicola Vinti, lamellibranchs 

 generally regarded as freshwater forms." Kirkby, as his habit was, 

 gave an accurate description of the organism, and one can add little 

 to his diagnosis, which is as follows: " length one-twelfth to one- 

 eighth of an inch, breadth one-fourteenth to one-tenth, sub-oval or 

 nearly circular, with the posterior margin straight, flatly patelliform, 

 with an eccentric reflexed apex posteriorly placed, shell delicate, 

 surface ornamented with several rather coarse concentric plaits." 



I am much indebted to Mr. H. Bolton, M.Sc, F.G.S., to whom 

 I submitted some of the specimens for the suggestion that these 

 organisms are the " spat " of Anthracomya Phillipsi. He writes: 

 " I have examined the fossils you sent me, especially the example of 

 ' Ancylus ( Carbonicola) ' Vinti, and have found them of more than 

 usual interest. In the first case I fail to see any Carbonicola 

 character at all in any of them : what I do see, is that so far as my 

 experience goes, you are dealing with 'spat' and not with adult 

 forms of mollusca. I gave a long time to the study of the life- 

 history of Anthracomya Phillipsi, and had the advantage of a great 

 series of specimens from several coalfields, whilst I had the 

 experience of thirty years to aid me. I feel convinced that your 

 specimens and the Ancylus (' Carbonicola'') Vinti are nothing but 

 the spat of Anthracomya Phillipsi. As you will see by my paper, 2 

 I have linked three former species, viz. Anthracomya Icevis var. 

 Scotica; A. minima; and A. Phillipsi. The first is the 'spat' 

 stage, the second the adult stage, and the third the senile stage 

 of the one species. I shall be interested to learn whether your 

 Ancylus Vinti ever occurs away from the Anthracomya Phillipsi. 

 Of course it may, but I think you will find the other two species not 

 far off. The ' spat ' stage has usually a short straight hinge-line, and 

 the valve is perfectly symmetrical to it and not oblique at all; the 

 obliquity comes in with the '■minima'' stage. Until the latter is 

 reached the central and youngest part of the umbones remains fairly 

 elevated and convex. As the ' minima ' stage increases the new 

 shell matter is added to the ventral-posterior border at a much 

 greater rate than elsewhere, and as a result there is an increasing 

 obliquity, which reaches its maximum in the l Phillipsi , stage. 

 I have seen shells so well preserved that you can mark off the three 

 stages on the surface on the one shell." 



1 Les Piriodes GAologiques, vol. ii, p. 764. 



2 "Fauna and Stratigraphy of the Kent Coalfield": Trans. Inst. Mining 

 Engineers, vol. xlix, pt. iv, p. 33, 1915. 



