170 BRITISH CARBONIFEROUS BRACHIOPODA. 



Spec. Char. Marginally rotundato-quadrate, generally wider than long, lateral margins 

 sub-parallel ; rounded or slightly indented in front ; hinge-line rather less than the greatest 

 width of the shell. Ventral valve convex, with a wide, shallow, median depression or 

 sinus ; beak incurved, not overlying the hinge-line, except at its attenuated extremity ; 

 ears small, flattened. Surface covered with numerous sub-regular striae, swelling out at close 

 intervals in the shape of oblong tubercules, arranged somewhat irregularly in quincunx, and 

 from each of which rise slender, curved spines, of rather less than half an inch in length ; 

 feeble concentric wrinkles sometimes traverse the valve, and are especially marked on the 

 ears. Dorsal valve concave, near the margin, with a slight median elevation commencing not 

 far from the front; surface covered with numerous concentric wrinkles, tubercule-pits, and 

 short, depressed, slender spines. Dimensions variable ; two British examples measured' — 



Length 28^, width 33^ lines. 

 12 12 



Obs. Variations in shape of this shell have received different names, and it has been 

 sometimes suggested that it and the preceding species should be united. 1 Professor de 

 Koninck mentions that it bears much resemblance with the young state of his P. pyxidi- 

 formis, and that it approaches likewise to P. Humboldtii, and I am ready to admit that a 

 certain external resemblance does sometimes exist among certain examples of these species. 

 In true P. scabriculus the swollen-out, alternating, elongated tubercules are connected by 

 a continued ridge, so that the shell has the appearance of being ribbed, while in P. pustu- 

 losis the tubercules are more often isolated. The interior, however, in the dorsal valve 

 presents a difference in the shape of the median ridge, which extends from under the 

 cardinal process and divides the adductor impression. In P. pustulosus this ridge is 

 simple, while in P. scabriculus it is composed of two ridges, which converge and unite at 

 some distance from their origin into a single ridge (fig. 8). I have observed this character 

 in several examples, and believe it constant. 



P. scabrivalm is common in the Carboniferous limestone of the Craven district, and 

 Settle, in Yorkshire ; near Bolland ; in dark Carboniferous limestone at Lowick, 

 Northumberland ; Martin found it in the limestone of Tideswell, in Derbyshire. It is not 

 uncommon at Coalbrook Dale ; near Bristol, &c. In Scotland, it is plentiful in ironstone 

 at Jock's Burn, Braidwood, Brockley, and many other Lanarkshire localities. In Stirling- 

 shire it occurs in several stages, such as the Craigenglen beds, Campsie main-limestone 

 and ironstone, and at Corrieburn. It has also been found in Renfrewshire, Dumbarton- 

 shire, Ayrshire, the Lothians, and Fifeshire. In Ireland, Mr. Kelly mentions that it occurs 

 in the Calciferous slate and Carboniferous limestone of Lisnapaste, Millecent, Little Island, 

 and of, no doubt, many other localities. It is also a common fossil on the Continent, 

 having been found at Vise, in Belgium ; Peredki (Valdai), Sloboda, &c, in Russia. 

 Specimens have also been collected in America, &c. 



1 Explanations to accompany sheets 102 and 112 of the maps of the Geological Survey of Ireland. 

 p. 1G. 



