94 CARBONICOLA, ANTHRACOMYA, AND NATADITES. 
narrow, V-shaped trench between the opposing valves, the continuation of the 
slight groove along the border of the shell which gives attachment to the external 
hgament. 
Dimensions. —The type-specimen (Pl. XIII, fig. 4) measures— 
Antero-posteriorly. Dorso-ventrally. From side to side. 
48 mm. (restored) 29 mm. (near posterior end). 20 mm. 
Fig. 5, Pl. XIII, 51 mm. 32mm. 23 mm. 
Localities. —Pennystone beds, Coalbrookdale. Little Mine (Burnwood) 
Ironstone, North Staffordshire. Black Mine Middle Coal-measures, Oldham, 
Lancashire. 
Observations —This species was one of the two members of the genus first 
described and figured, and I am fortunately able to refigure the original 
specimen through the kindness of Professor Prestwich, who has lent me the fossil 
for examination. The anterior end is absent, a fact which was shown in the 
original drawing by James de Carle Sowerby (op. supra cit.), the lines of growth 
anteriorly ending abruptly, although this incompleteness was not noted in the 
description, where it is stated, “‘ Anterior side small, rounded; . . . . beaks near 
the anterior side.” Mr. Salter, judging hastily from the figure alone, says in his 
original description of the genus Anthracomya, ‘‘ A. dolabrata (Sow.) is still 
more convex [than A. Adamsii], and has an almost obsolete anterior side” (op. 
supra cit.). 
Anthracomya dolabrata is very closely allied indeed to A. Adamsii, and in North 
Staffordshire the two species are found together in the Burnwood Ironstone. 
On the other hand, there is a strong resemblance to certain large forms of A, 
modiolaris, so that it forms a connecting link between these species. 
From A, Adamsii, Anthracomya dolabrata differs in its much greater convexity, 
being the most gibbose species of this genus, by the greater tumidity and height 
of the umbones. The greatest thickness is suabumbonal, not as in A. Adamsii about 
the centre of the shell; and reiatively the antero-posterior measurement is greater 
than in A. Adamsii. But forms occur intermediate in shape and character between 
the two,—for example, fig. 6, Pl. XIII. 
I have seen nothing in Continental museums which can be considered at all 
like the species under description; and, indeed, the shell has been very little 
noticed by palzontologists. Salter dismisses it in one line, and Captain Brown 
simply copied Sowerby’s figure, giving a very inaccurate description, and stating 
the locality as Coalbrookdale. It is very evident that he never saw any specimen 
of the shell in question. 
In my paper “ On the Affinities of Anthracoptera and Anthracomya” (‘ Quart. 
Journ. Geol. Soc.,’ vol. xlix, p. 261) I re-described the species from the type 
kindly lent for that purpose by Prof. Prestwich, and I then stated that certain 
