PRODUCTUS. 169 



of the shell under description, there can exist but little doubt that P. rugata, P. ovalis, and 

 P. pyxidiformis, are merely different states of P. pustulosus, and I quite coincide with 

 Professor M'Coy when stating that " scarcely any two examples of P. pustulosus agree in 

 the strength or directness of the transverse ridges ; in specimens perfectly typical in this 

 respect near the beak, the ridges will be often found indistinct, undulated, and interrupted 

 on other parts, and when this is the case the tubercules generally increase in size and be- 

 come quincuncially arranged. I have traced the passage from the most regularly wrinkled 

 type (like Koninck's figure, op. cit., t. xii, fig. 1), with the spines on the summits of the trans- 

 verse ridges, through those in which the spines do not coincide with the (still well-marked) 

 ridges (like his t. xvi, fig. 9), to those in which the wrinkles gradually become irregular, 

 interrupted, and nearly obsolete, as VbP.pyscidiformis, by the most imperceptible gradations. 

 In all these varieties the isolation of the tubercules, instead of their being mere inflations of 

 distinct, longitudinal stria? or ridges, distinguishes the species from the true P. scnbricula." 

 I have never yet obtained a perfect specimen of the shell under description, for in all 

 the British examples the spines were broken close to their base. 



The interior has been sometimes obtained, and of which figures are given in my plate. 

 In the umbonal portion of the ventral valve the occlusor or adductor scars are placed on 

 either side of a small ridge between and on a level with the cardinal or divaricator im- 

 pressions. In the dorsal valve the adductor and riniform impressions do not differ much 

 in detail from what we find in the generality of Producta. P. pustulosis is not rare in 

 the Carboniferous limestone of many English localities, such as Holland, Settle, Kendal, 

 the Isle of Man, in Derbyshire, &c. In Scotland it has been stated to occur at Cat Craig, 

 near Dunbar. In Ireland in the Calciferous slate and Carboniferous limestone of 

 Bundoran, Ballyduff, Carrigaline, Lisnapaste, Millecent, Tankardstown, Florence Court, 

 Little Island, shores of Lough Gill, valley of the Maine, Hook. St. Doolas, near Dublin, &c. 



On the Continent it occurs at Vise and Tournay, &c, in Belgium ; Ratingen (Prussia) ; 

 and it has also been found in America. 



Productus scabriculus, Martin. PI. XLII, figs. 5 — S. 



Anomites scabriculus, Martin. Petrif. Derb., p. 8, pi. xxxvi, fig. 5, 180!). 

 Productus — Sow. Min. Conch., t. Ixix, fig. 1, Oct., 1814. 



Producta scabricula, Phill. Geol. of York., vol. ii, pi. viii, fig. 2, 1836. 



— quincuncialis, PAUL lb., pi. vii, fig. 8. 



scabriculus, De Koninck. Desc. des Anim. foss. du Terrain Carb. de Belg.. 

 pi. xi, fig. 3 "• s (?), 1843 ; and Mon. du genre Productus, pi. xi, 

 fig. 6, 1847. 



— corbis, Potiez et Michaud. Galer. des Mollusques du Mus. de Douai, vol. ii, 



pi. xli, fig. 2, 1844. 



— scabriculus, De Verneuil. Russia and the Ural Mount., pi. xvi, fig. 5 ; and 



pi. xviii, fig. 5, 1845. 

 _ _ M'Coy, British Pal. Fossils, p. 470, 1855. 



_ _ Bav. Scottish Carb. Brach., pi. iv, fig. 18, 1861. 



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