EDMONDIA SULCATA. 321 



casts of A. sulcata have not ; E. sulcata has external radiating striae formed of 

 rows of minute tubercles, while A. sulcata also has this form of marking, 

 rendering the mimicry more perfect. King quotes a letter from Fleming (op. 

 supra cit., p. 163) in which he says, " Two of the shells do certainly resemble my 

 Hiatella sulcata. On one of the casts there are traces of the strias, a character 

 rarely to be met with, owing to the extreme thinness of the shell, and its usual 

 imperfectly preserved state." Mr. Neilson has a fine series of Allorisma sulcata 

 from the Garngad Road strata of Glasgow, which show the external markings 

 very well, but the shells are at once distinguished from Edmondia by the well- 

 developed elongate escutcheon and the presence of a definite lunule. 



Phillips states that his S. sulcata came from Redesdale, and I cannot trace the 

 original. In the York Museum there are four good examples which belonged to 

 the Yorkshire Physical Society, and which are labelled " Richmond," one of 

 which I think is very probably the type specimen. I figure it PI. XXXIV, fig. 3. 

 J Phillips's description is very meagre, and does not mention the bifurcation of 

 the concentric folds in front, though the lower part of his figure shows them ; and 

 the umbones are not anterior enough for A. sulcata. 



King, it appears, had originally placed both shells in the genus Allorisma 

 ('Ann. Mag. Nat. Hist.,' Nov., 1844), but Morris pointed out that one of these 

 did not possess a sinuated pallial sinus (Strzelecki's 'Physical Description, New 

 South Wales,' p. 270) ; and therefore, in the ' Monograph of Permian Fossils,' 

 King mentions that he considered the shell should be referred to Edmondia, 

 de Koninck. Although no fresh description was given, there are good figures of 

 the shell and its peculiar expanded ossicle ; in fact, the generic character of this 

 appendage is induced from this species. The ossicle is, however, apparently far 

 better developed and more differentiated in E. sulcata than in any other species 

 of the genus. 



M'Coy gave a long description of the species (op. supra cit.), and described 

 accurately the relation of the ossicle to the muscle-scars. He, however, seems to 

 have misunderstood King, for he correctly describes the pallial line as " perfectly 

 entire," as did that author ('Monograph of Permian Fossils,' p. 163), but M'Coy 

 adds, " so that Mr. King must have been deceived in this respect." Perhaps, 

 however, M'Coy had not taken the trouble to consult this work of King's, 

 published several years before his own, and was basing his criticism on the 

 preliminary notice in the ' Ann. and Mag. Nat. Hist.,' noted above. 



The specimen of E. sulcata figured by King is preserved in the museum of 

 Newcastle-on-Tyne, but I am unfortunately not permitted to refigure it. The 

 umbones which King had knocked off, so as to expose the ossicle, have beeii 

 cemented on, so that this feature is not visible to the visitor. I have fortunately 

 been able to figure an example from the collection of Mr. Morton, of Liverpool, 



