SANGUINOLITES ROXBURGENSIS. 407 



is a rounded ridge, which separates the compressed dorsal slope from the rest of 

 the valve, which is convex from above downwards and from before backwards. 

 The lunule is small and the escutcheon narrow-elongate, separated from the 

 dorsal slope bj an erect curved line. 



Interior. — The anterior adductor muscle-scar is small, round, placed just within 

 the autero-superior angle, and has a shallow ridge posterior to it. The posterior 

 adductor scar is large, rough, and placed immediately below the hinge-line, but 

 remote from the posterior end. The pallial line is entire. The hinge-line 

 appears to be edentulous. The interior of the shell is marked by concentric 

 grooves and rugre. 



Exterior. — The surface is ornamented with fine concentric strisB, interrupted 

 here and there by a deeper line, dividing the striae into groups. Shell thin. 



Dimensions. — PI. XLVT, fig. 12, measures — 



Antero-posteriorly . . . .14 mm. 



Dorso-ventrally . . . .7 mm. 



From side to side . . . .5 mm. 



Localities. — Scotland ; a bed of black Limestone crammed with Lamelli- 

 branchs, Black Burn, New Castleton, Roxburghshire; Calciferous Sandstone 

 series. Ireland: the Carboniferous Limestone of Grillage Bridge, co. Clare. 



Observations. — This species is of small size, and occurs in the Scottish locality 

 in large numbers in association with Modiola MacAdamii. The oblique fold is 

 not very pronounced, and the shell appears to be somewhat narrowed posteriorly. 

 A shell is figured in the Explanatory Memoir of Sheet 127 of the Geological 

 Survey map of Ireland, which may possibly be identical with 8. roxhurgensis. 

 T!ie type specimen is, however, nothing at all like the original drawing, con- 

 sisting of a very poor flattened impression of a left valve, incomplete at the 

 posterior end. The woodcut {op. cit.) shows a left valve free from the matrix. 



Most of the New Castleton specimens are casts, and possess a high polish ; 

 but a few possess the shell preserved. The collection of the Geological 

 Survey of Scotland possesses a number of specimens ; and Owens College, 

 Manchester, has a fine slab crammed with Protoschizodus axiniformis, Modiola 

 MacAdamii, and 8. roxhurgensis. Imperfectly freed from the matrix, the shell 

 may often appear to have a pointed posterior, and to possess a Unio-like form. 



