82 CARBONICOLA, ANTHRACOMYA, AND NAIADITES. 
Exterior.—The shell is ornamented with distinct but fine lines and stria of 
growth somewhat oblique to the long axis of the shell. 
Dimensions.—Fig. 15, Pl. XX, measures— 
Antero-posteriorly : . . . 20 mm. 
Dorso-ventrally : 5 ; . 10mm. 
Locality —Lower Cement-stone series, Fife; Limestone No. 10, at Rander- 
stone, in a three-inch band of calcareous ironstone in light-grey sandy slate; in 
cliffs east of Pittenweem. 
Observations.—This species was described by Mr. Kirkby, in his careful and 
accurate paper on the Marine Zones of the Calciferous Sandstone Series of the 
Fifeshire coast, under the name of Plewrophorus elegans, the generic name being 
given on the authority of Prof. de Koninck. He has kindly lent me a series of 
his fossils for study, and I have been able to examine the hinges and casts of the 
interior, with the result of coming to the conclusion that his shell belongs to the 
genus Carbonicola. The form of the hinge is practically identical with the type 
found in Carbonicola aquilina, and this differs markedly from the form found in 
Pleurophorus, which King states (Paleontographical Soc. vol. for year 1849, 
“Permian Fossils,” p. 180): ‘Cardinal teeth two in each valve, diverging 
inwardly, and interlocking alternately ; posterior teeth linear.” Moreover, the 
species under discussion does not possess externally the radiating ribs on the 
posterior slope nor the characteristic shape, wider in a dorso-ventral direction 
posteriorly, which are to be seen in Pleurophorus. 
Carbonicola elegans possesses characters which also are found in the other 
species which occurs in the Calciferous Sandstone Series, C. antiqua. The 
bevelled inner edge of the posterior border and other hinge peculiarities are 
similar in both, but there is no doubt that they are not the same species, differing 
so markedly from each other in shape and form. 
Mr. Kirkby describes a faint diagonal ridge running from each umbo towards 
the postero-ventral angle, which I have been unable to make out in any of the 
specimens sent me, but otherwise his description is very accurate. 
The shell more closely resembles C. aquilina than any other species, having in 
common with it the lines of growth arranged obliquely to the long axis of the 
shell, and the upper border of the anterior end being much below the level of the 
umbones ; also the hinge characters are very similar ; but Carbonicola elegans is 
more cylindrical, and has its umbones curved inwards, downwards, and forwards. 
In the same beds with C. elegans only one other Molluse is found, Littorina 
Scotoburdigalensis, but Leperditia Okeni, var. attenuata, and Oytherella also occur 
—a very similar fauna to that which accompanies O. antiqua; and it is very 
noticeable that the typical marine forms so abundant in the other shell-beds of the 
Fifeshire coast are conspicuously absent. With regard to the shell called 
