PRODUCTUS. 229 



near Settle, in Yorkshire, are deserving of notice. In these specimens (PI. LIII, fig. 3), 

 the adductor or anterior occlusor scars of Hancock (A) are longitudinally striated, while the 

 posterior occlusors (A') are clearly defined and dendritic in their markings. 



Orthis (pp. 129—135). 



I can add nothing to what has been already said with reference to the species com- 

 posing this genus, except that Orthis (}) antiquata must still remain among the doubtful 

 so-termed species, for only one or two specimens of it have been hitherto found. 



Productus (pp. 135 — 179). 



Twenty-eight species ? and a few named varieties have been here described ; but, sub- 

 sequently, five more new to England were discovered by Mr. Burrow in the Carboniferous 

 Limestone of Settle, which we will at once proceed to describe. 



Productus marginalis, De Koninck (PI. LIII, fig. 3). 



Productus marginalis, De Koninck. Monographie du genre Productus, pi. xiv, fig. 7, 



1847. 



Sp. Char. Shell thin, circular, or sub-trapezoidal ; slightly wider than long, somewhat 

 geniculated and gibbous, with a narrow, projecting, curved margin ; hinge-line rather less 

 than the greatest width of the shell, with a small rudimentary area ; beak small ; ears 

 flattened ; surface wrinkled over the visceral portion of the shell, and irregularly inter- 

 rupted, here and there, by prominent tubercules, which give rise to slender spines ; while 

 on the anterior portion of the curved margin the wrinkles of the visceral portion are re- 

 placed by small contiguous ribs ; dorsal valve almost flat, concave only, or suddenly bent 

 close to the margin ; surface slightly marked by concentric wrinkles, which are replaced 

 by small ribs near the margin ; little pits are likewise dispersed over its surface. Interior 

 muscular and other markings agreeing with those of the generality of Producta. Dimen- 

 sions variable. 



Length 8, width 9 lines. 



Obs. The discovery of this Productus, as a British species, is due to Mr. Burrow ; and 

 in order to be quite certain as to its identity, the specimen here figured was fowarded to 

 Prof, de Koninck, who confirmed the identification. In England it appears to be a rare 

 species. It was obtained from the Lower Scar Limestone of Settle, in Yorkshire. At Vise, 

 in Belgium, it is not rare in the state of internal casts, four or five specimens 

 only have been found by Prof, de Koninck with the shell completely preserved. 



