SANGUINOLITES LUXURIANS. 403 



or less well-marked rounded ridge passes from tlie umbo obliquely backwards and 

 downwards to the posterior angle, separating a small but rapidly compressed 

 dorsal slope. Anterior to the ridge the valve is convex from above downwards, 

 and before backwards, with a feeble, oblique, broad constriction about its centre, 

 passing from the umbo to the inferior border. The dorsal slope is crossed near 

 its upper part by a feeble radiating line, above which is an elongate groove, 

 which commences as a narrow depression at the umbo, and becoming deeper and 

 broader as it passes backwards, terminates at the posterior margin. The groove 

 is bounded above by an erect fold, the upper edge of which is curved and forms 

 the outer boundary of the large elongate escutcheon. External ligament small 

 and short. 



Interior. — Details of the anterior adductor muscle-scars and the hinge are 

 unknown. The posterior adductor muscle-scar is large, shallow, pear-shaped, and 

 placed in the hollow of the dorsal slope, remote from the posterior end. Pallial 

 line entire. 



Exterior. — The surface is ornamented with fine concentric strise and lines of 

 growth, a deeper one here and there interrupting the regularity of the markings, 

 which are more pronounced on the dorsal slope and near the inferior border. 



Dimensions. — PI. XLVI, fig. 4, from Lisbane, co. Limerick (in the collection 

 of the Geological Survey of Ireland), measures — 



Antero-posteriorly . . . .74 mm. 



Dorso-ventrally • . . .34 mm. 



From side to side (estimated) . . .34 mm. 



Localities. — England: the Carboniferous Limestone of Poolvash, Isle of Man. 

 Ireland : the Carboniferous Limestone of Lisbane, co. Limerick, and Ardfodien, 

 CO. Kildare. 



Observations. — De Koninck founded the species S. luxurians on a very perfect 

 and finely grown shell from the Carboniferous Limestone of Tournay, and I am 

 pleased to record the presence of this fine species from two localities in Ireland. 

 PI. XLVI, fig. 4, is a testiferous example of the left valve; and PI. XLYI, fig. 5, 

 is the cast of the interior of the left valve. The oval shape, narrowed anterior 

 and posterior ends, oblique gibbosity, and small dorsal slope, without radiating 

 lines, I regard as characteristic features for the diagnosis of the species. De 

 Koninck has placed this species in his group of the Sanguinolites having two folds 

 on the dorsal slope, which in this case evidently are represented by the oblique 

 ridge, and the ridge below the groove beneath the upper margin. These ridges, I 

 think, are in no way analogous to the radiating lines of 8. tricostatus, S. visetensis, 

 and 8. ohlongus. 



Sowerby described and figured a shell from the Carboniferous Limestone of 

 Queen's County, Ireland, under the name 8anguinolaria gibbosa {op. cit.). The 



