SANGUINOLITES VARIABILIS. 381 



Localities. — England : the Redesdale Ironstone Shale, Redesdale, and a bed of 

 Limestone at Lowick, Northumberland. 



Observations. — There can be no doubt tliat M'Coy founded his species 

 Sanguinolites variabilis upon two quite distinct shells, one of which does not even 

 belong to the genus, but should be referred to Allorisiiia, for the reason that 

 certain specimens of the same species have a well-marked pallial sinus, i am 

 able to re-figure both the type specimens, and I have had them drawn on the 

 same plate for the sake of comparison (PI. XLIV, figs. 1 aud 2). It will be at 

 once seen that the two shells differ materially in shape, contour, and the character 

 of the surface-markings. The first, therefore, of M'Coy's figures must take the 

 name Allorisma variabilis ; while I propose to retain the name Sanguinolites 

 variabilis for the second. 



M'Coy's figure of the former shell is drawn largely from imagination. The 

 type specimen is imperfect in front, and has the matrix still unremoved in front 

 of the umbones, so that the lunule is invisible ; and the shell is evidently iu- 

 coraplete in front along the lower margin. M'Coy called his second figure an 

 ovate variety, but this form is not at all uncommon in the Redesdale Ironstone 

 series. As is usual with M'Coy's figures, the shell, a left valve, appears on the 

 plate as a right valve, no allowance having been made for the reversion of the 

 figure during the process of printing. 



M'Coy compares his species with Edmondia sulcata, but these two species are 

 not likely to be confused, the absence of lunule and escutcheon in Edmondia at 

 once serving to distinguish the two shells ; and, in addition, the surface-ornaments 

 are totally different with regard to the arrangement of the sulci and ridges. 

 M'Coy notes that the " periostracum is sharply marked with close interrupted 

 striae and a few minute scattered points, very rarely falling into close regular 

 radiating lines." I have not been able to make out that 8. variabilis possesses 

 this character, though it is certainly present in Allorisma variabilis. 



M'Coy gives three localities for his double species : the Lower Limestone of 

 the Isle of Man, Lowick, Northumberland, and Berwick-on-Tweed. I am unable 

 to recognise any Manx shell which could be referred to either of the species, and, 

 unfortunately, there is no evidence to show to which of the two specimens the 

 Berwick shell belonged. 



Sanguinolites variabilis much more nearly approaches 8. costellatus in character, 

 but the valve is not so curved from above downwards, and the dorsal slope is 

 much less hollow and expanded from side to side, being more vertical in 

 position and compressed. The surface-markings are much finer and the ribs more 

 numerous in the latter species. 



M'Coy states that the ovate form of this shell has no byssal sinus; but there 

 is a well-marked compression in several of my specimens, which passes from the 



