Yd. 56.] PALJEONEILO IN" BRITISH CARBONIFEROUS ROCKS. 49 



The anterior part of the lower margin is much incurved, but 

 gradually, being twisted outward on itself, becomes flattened and 

 depressed in its posterior half. 



Interior. — The muscle-scars and pallial line have not been 

 observed. The hinge is multidenticulate, and the hinge-plate is 

 much thickened. Anteriorly there are several (seven) large oblique 

 simple teeth, becoming larger as they approach the front, with the 

 exception of that one which is placed most anteriorly. These pass 

 just behind the umbo into a number of vertical, much smaller, closely- 

 placed, comb-like, simple teeth, which extend for some distance 

 behind the umbo, and then gradually become larger and oblique 

 in position, each tooth slanting downward and forward, and 

 becoming more widely separated from its neighbour, the row of teeth 

 extending to within a small distance of the postero-superior angle. 



Exterior. — The surface is ornamented with fine close lines of 

 growth, which follow accurately the contour of the shell, being 

 oblique to its long axis, and are more marked in the region of 

 the umbo, and on the dorsal slope, where they may become sub- 

 imbricate. 



Dimensions. — The specimen figured measures antero-posteriorly 

 57 mm., and dorso-ventrally 27 mm.; convexity of valve = 12 mm. 



Locality. — England, in shales above the main mass of limestone 

 in the beck, south of Hammerton Hall, Slaidburn (Yorkshire). 1 



Observations. — Ctenodonta (Palceoneilo) lirata (Phill.), from 

 the Devonian of Baggy, has much the same kind of surface-marking 

 as P. carbonifera, but differs entirely in shape ; indeed, this species 

 is quite distinct from any of the shells belonging to the same genus, 

 either from European or American Devonian localities. I am 

 unable to say anything about the fauna associated with P. carbonifera 

 at present, but beds of shale on presumably the same horizon at 

 "White well, a few miles farther south, contain the following fossils: — 

 Ctenodonta sinuosa, Nuculana attenuate* , Parallelodon semicostatus, 

 Modiola sp., Glauconome, Fenestella sp., Retipora pluma, Phill., 

 Glyphioceras spirale, and Ortlds Michelini. 



Discussion. 



Mr. "Walcot Gibson said that he was pleased to see that the Author 

 found opportunity, amidst a busy professional life, to add from time 

 to time to our knowledge of the lamellibranch fauna of the Carboni- 

 ferous system. The absence of a Palceoneilo from the lowest beds 

 of the Carboniferous Limestone was possibly accounted for by the 

 really little palseontological work that had as yet been done, con- 

 sidering the great development of the Lower Carboniferous rocks in 

 England and Wales. Further research would no doubt fill up 

 many gaps. 



Mr. E. S. Herries, Dr. G. J. Hinde, the Rev. G. F. Whidborne, 

 and Mr. Strahan also spoke. 



1 [The specimen -was collected and labelled by Mr. Gibbs, late fossil-collector 

 to the Geological Survey.] 



Q. J. G. S. No. 221. e 



