CARBONICOLA VINTT. 145 



Exterior. — The surface is smooth and glistening, covered with fine concentric 

 lines and folds. Periostracum much wrinkled. Shell thin. 



Dimensions. — PL XXV, fig. 19, measures : — 



Antero-posteriorly . . . .5 mm. 



Dorso-ventrally . . . .3 mm. 



Localities. — In a calcareous bed some yards above the Bassey Mine Ironstone, 

 in an old marl-hole near Chatterley Station ; in calcareous bands about ten yards 

 above the Bassey Mine Ironstone, the Hamil, Burslem, Upper Coal Measures, 

 North Staffordshire; in a bed of ironstone in the northern bank of the Wear, 

 opposite Claxheugh, Upper Coal Measures, Durham. 



Observations. — A very full account of the history of the discovery of this fossil 

 is given by Mr. J. W. Kirkby (op. supra cit.), who was disposed to admit the 

 lamellibranchiate character of the little shell, which was considered by some high 

 authorities to be a gasteropod (Ancylus), by others to be a brachiopod allied to 

 Discina, and was thought by yet others to be a crustacean. 



I have referred my specimens to Mr. Kirkby, Prof. T. Rupert Jones, and 

 Dr. (1. J. Hinde, with the following result : the latter two gentlemen consider 

 that the shell is a lamellibranch, and Mr. Kirkby writes that it is identical with 

 his Ancylus Vinti. The specimens that I have of Ancylus Vinti from the Durham 

 beds, kindly sent by Mr. Kirkby, seem to me to be simply the closely-compressed 

 remains of the periostracum of a large number of shells, a circumstance which 

 probably accounts for the difficulty in accurately determining the fossil. 



Fortunately the North Staffordshire specimens are much better preserved, and, 

 though generally somewhat crushed, show the general outline and character of the 

 shell, and are therefore more easily referred to their real family and genus. After 

 discussing the question of the true affinity of this shell at length (pp. supra cit.), 

 Mr. Kirkby finishes by saying : " For the present, therefore, it will be as well, 

 perhaps, to retain as a provisional name Prof. Phillips's term of Ancylus. This 

 I propose chiefly to get rid of the evil of having an unnamed fossil . . . and not 

 because I am of the opinion that it really belongs to Ancylus. For, whether it be 

 an entomostracan or a mollusc, the evidence certainly would appear to go towards 

 proving that it had a bivalvular rather than an univalvular carapace." 



Oarbonicola Vinti would appear to be the last representative of this well- 

 developed and frequently recurring Carboniferous fresh-water genus, and to occur 

 at a higher horizon than any other species of the genus. As Mr. Kirkby points 

 out is the case in the Durham beds, this fossil is associated in North Staffordshire 

 also with a non-marine fauna. He estimates that Garbonicola Vinti occurs at an 

 horizon not much over 50 or 60 feet from the top of the Coal Measures or the 

 base of the Lower Red Sandstone, but in North Staffordshire there is a thickness 

 of several hundred feet of red and purple beds of the Upper Coal Measures above 



