PRODUCTUS. 177 



of our plate, which represents an internal east of the ventral valve, on which the adductor 

 and divaricator impressions are well marked. The interior of the dorsal valve does not 

 appear to have been hitherto discovered, at least no example has come under my observa- 

 tion. From P. sub-lavis the form under description is distinguished by its transverse 

 shape and much smaller dimensions, &c. 



In England it is found in the Carboniferous limestone of Settle, in Yorkshire ; the 

 gray or lower limestone of Longnor and C'astleton, in Derbyshire. In Ireland Mr. 

 Kelly mentions that it occurs in the limestone of Armagh, Salmon, and Little Island. No 

 specimen from Scotland has been hitherto produced, but it is very common in the 

 limestone of Vise, in Belgium, as well as in the dark limestone of Ilof, in Bavaria, and 

 Falkenberg, in Silesia. It has also been stated to occur in Russia, but was not met 

 with there by the authors of the ' Travels in Russia and Ural.' 



Productus sub-l.evis, De Koninck. PI. XXXI, figs. 1, 2 ; PI. XXXII, fig. I ; and 



PI. LI, ligs. 1, 2. 



Productus SUB-LJEVIS, De Koninck. Descvipt. des Anim. foss. du Terr. Garb, de Belgiquo, 



pi. x, lig. 1, 1813. 

 Strophomena axtiquata, Potie: et Mich. Galer. des Moll, de Douai, vol. ii, pi. xlii, fig. 5? 



1 84 1 (according to De Koninck). 

 Pkoductus sub-l.evis, De Keyserling. Peise in das Petschora Land, pi. v, figs. 3 and 3", 

 181G. 

 — Christian:, De Koninck. Monographic du genre Productus, pi. xvii, fig. 3, 



1847. 



Spec. Char. Shell elongated, oval, sub-quadrangular, and longer than wide; hinge-line 

 about as long as the greatest width of the shell. Ventral valve gibbous, much vaulted 

 upon itself at the beak, and longitudinally divided by a median groove or ridge, which 

 commences to appear at a short distance from the beak, and extends to the front, 

 while the lateral portions of the valve are more or less deeply furrowed ; ears moderately 

 developed, sub-cylindrically coiled, and sharply defined from the body of the shell by a row 

 of tubular spines. Externally the visceral portion of the valve is traversed by numerous 

 concentric, feebly marked wrinkles, while the entire surface is longitudinally and finely 

 striated. Dorsal valve concave, following the curves of the opposite valve, and similarly 

 sculptured. Interior unknown. Dimensions variable; two British examples have 

 measured — 



Length 4 inches 8 lines, width 4 inches 1 line. 



Obs. This remarkable Productus varies much in appearance, according to age and 

 specimen. When the external coat or surface is well preserved, it is very finely striated, as 

 well as crossed by many concentric lines of growth, but when the outer surface has been 

 removed by fossilisation the shell appears to be almost entirely smooth. Some examples 



23 



