332 ME. HEEBEET BOLTON ON [Aug. I9II r 



Naiadites cf. carinata (Sowerby). (PI. XXVII, fig. 15.) 



The cast of a pair of attached valves and two larger crushed 

 valves were found in a dark shale at Easton Colliery. I consider 

 them to be examples of this species. The attached valves, though 

 small, and in the condition of internal casts, are in very good pre- 

 servation, the anterior adductor muscle-scar impression standing up 

 in relief upon the left valve. The umbones are small, in apposition, 

 and angulated. An oblique ridge passes backwards from the umbo 

 to the posterior ventral border, broadening out towards the latter. 

 In front of the oblique ridges, the cast shows a shallow fold deepen- 

 ing anteriorly and ending under the umbones, imparting to the latter 

 a pinched appearance when viewed from the front. The crushed 

 valves are 10 millimetres long. 



Horizon and localitj 7 . — Black Shale, Easton Colliery. 



Naiadites sp. 



The impression of a Naiaclites somewhat resembling N. elongata 

 occurs in well-bedded Lower Coal-Measure black shale, in associ- 

 ation with Antliracomya ivilliamsoni, from the Speedwell Colliery, 

 Kingswood, Bristol. 



PSEUDOEDMONDIA (?) Sp. nOV. (PI. XXVII, fig. 16.) 



Considerable interest attaches to this specimen, owing to the rarity 

 of occurrence of luciniform mollusca in the Carboniferous formations. 

 Only one specimen was found, in a dark-grey Upper Coal-Measure 

 shale at Writhlington Colliery, Radstock. It consists of two 

 attached valves having a length of 8 millimetres, and a depth of 

 6 mm. in the right valve, which is almost fully exposed. The 

 umbones are small, incurved, a little anterior to the centre of the 

 hinge and directed forwards. They are moderately tumid, and 

 encroach upon, but do not hide, the hinge-line. A small elongated 

 lunule lies in front of the umbones. The hinge-line is straight, a 

 little less than the greatest length of the shell, and passes into the 

 anterior and posterior borders at an obtuse angle. The anterior 

 border curves forwards and downwards from the hinge-line, and 

 passes in a well-rounded curve into the ventral border, which is 

 but slightly convex in outline. The posterior border is regularly 

 rounded. The general appearance of the valve is that of a broad 

 oval. The valves are somewhat tumid, the elevation of the umbones 

 spreading out equally in all directions to the middle of the shell, 

 from which it gradually dies out in the margin. The ligament 

 is thin, slightly elevated and rounded, and passes forward, dis- 

 appearing between the umbones. The surface of the shell is 

 smooth, but shows under magnification a series of concentric lines 

 of growth, well spaced out over the middle of the valve, and 

 crowded together along the anterior and posterior borders. 



Horizon and locality. — In massive dark-grey shale, Upper 

 Coal-Measures, Writhlington Colliery, Radstock. 



