PRODUCTUS. 150 



PltODUCTUS MARGAR1TACEUS, Phillips. PI. XLIV, figS. 5 8. 



Producta margaritacea, Phillips. Geol. of Yorksb., vol. ii, p. 215, pi. viii, fig. 8, 



1836. 



— PECTiNOiDES, Phillips. Ib„ pi. vii, fig. 11. 



— margaritaceus, De Kon. Desc. des Anim. foss. du Terr. Carb. de Belgique, 



pi. vii, fig. 3; pi. viii bi % fig. 5, 1843. Mon. du genre 

 Productus, pi. iv, fig. 3, 1847. 



— — De Keyserling. Wissensch. Beobacht. auf einer Keise in 



das Pctschora Land., p. 210, pi. iv, fig. 7, 1846. 



— — M'Coy. British Palaeozoic Fossils, p. 466, 1855. 



Spec. Char. Shell thin, somewhat circular or transversely semicircular, rarely longer 

 than wide ; hinge-line rather less than the width of the shell. Ventral valve regularly 

 convex, without sinus ; beak small, incurved ; ears narrow and but slightly distinguishable 

 from the general convexity of the valve; surface ornamented with numerous thick, 

 obtusely rounded or flattened ribs, separated by shallow sulci, the costse often bifurcating 

 near the margin, while the whole surface is closely crossed by concentric imbricating 

 striae, which at intervals produce strongly marked foliaceous interruptions or lines of 

 growth. The spines are few in number, but four or five strong ones project from each 

 of the auriculate expansions, while two or three more are sometimes irregularly scattered 

 over the surface. Dorsal valve concave, following the curves of the ventral one, and 

 similarly ornamented. Interior details imperfectly known. Dimensions variable; two 

 British examples have measured — 

 Length 15, width 18 lines. 

 „ 17, „ 16 „ 



05s. This is a well-marked species, easily distinguishable from its congeners, both by 

 shape and sculpture. Its shell is likewise remarkably thin and delicate, the ears very 

 brittle and often broken, while the space occupied by the animal between the valves is 

 very small. In shape it is more often transverse, and to this variety the name margaritacea 

 had been applied, while to the rarer or elongated form that of pcetinoides was given ; but 

 as every gradation in shape between the two can be readily found, a single specific 

 denomination can alone be retained. 



P. margaritaceus does not appear to be a very common species, and is confined to the 

 middle and lower stages of the Carboniferous system. In England it occurs at Bolland, 

 Kendal, Settle, in Yorkshire, as well as in some Derbyshire localities, &c. In Ireland it 

 may be obtained at Florence-court, Millecent, Kildare. Mr. Kelly mentions also 

 Lisnapaste, Bundoran, and one or two more places where it is said to occur. 



On the Continent it is not abundant in the Carboniferous limestone of Vise and Tournay 

 in Belgium, and has been found at Ratingen, D'Altwasser, in Silesia, and in one or two 

 Russian localities. 



