DAVIDSON — SCOTTISH CARBONIFEROUS BRACHIOPODA. 



19 



three hundred and seventj'five fathoms below the " Ell coal ;" occurs also at 

 Middlehohn, near Lesmahago and East Kilbride. In Stirlingshire at Corrie 

 Burn and Campsie main-limestone. In Renfrewshii-e at Orchard-quarry, near 

 Thornliebank:. In Ayrshire, at West Broadstone, Beith, and at Auchenskeigh, 

 near- Daby, etc. 



XIV. — Spiripeka Carlukiensis. Davidson. PL xii., fig. 29. 

 Spirifera Carlukiensis, Dav, Mon. Carb., p. 59, pi. xiii., fig. 14, 1857. 



Shell minute, nearly circular and smooth ; valves almost equally deep ; dorsal 

 valve regularly convex, most so at the umbone. Yeutral valve convex, with a 

 narrow mesial depression or furrow commencing at a short distance from the 

 extremity of the beak and extending to the front, where it indents the margin 

 of the opposite valve. The beak is small, pointed, and but sKghtly incurved ; 

 the hinge-liae much shorter than the greatest width of the shell, with its 

 cardinal angles rounded, area small, triangular. This little shell does not 

 appear to have ever greatly exceeded two lines in length by two and a-half in 

 breadth. It was discovered for the first time at Hill Head in Lanarkshire, at 

 about three hundred and fifty-six fathoms below the " Ell coal," along with 

 Sp. Urii, but it is a rare species, for m. every hundred or more specimens of 

 the last named shell that is collected, a single example of Sp. Carlukiensis would 

 occur. It has also been recently discovered near Strathavon in a bed of shale 

 almost entirely composed of Sp. Urii, and is there nearly as rare as at Hill 

 Head. 



XV.— Spirifera Urii. Eleming. PI. xii., fig. 30. 



Spirifer Urii, Eleming, British Animals, p. 376, 1828; Spirifera Urii, Dav. 

 Mon. Carb., p. 58, pi. xii., figs. 13, 14. 



This little species is sub-orbicular, and rather wider than long ; the hinge- 

 line shorter than the greatest breadth of the shell, and the cardinal angles 

 rounded. The dorsal valve is semicircular and slightly indented in front, with 

 a narrow hinge area ; it is nearly flat or slightly convex, especially at the um- 

 bone, from whence a shallow mesial fuiTOw extends to the front. The ventral 

 valve is much deeper and more convex than the ojDposite one, with a lengthened 

 incurved beak and longitudinal furrow, which, originating at the extremity of 

 the beak, is continued to the front. The area is small and triangular in shape ; 

 when perfect the exterior of the shell was covered with numerous closely im- 

 planted spines, but which are rarely preserved in the fossil, so that the shell is 

 generally found smooth or covered with minute pustulate markings, wliich are 

 produced by the fracture of the spines close to their bases. 



This abundant and interesting little species was noticed, and figured for the 

 first time by Ure, iu 1793, (History of Butherglen and East Kilbride, p. 313, 

 fig. 12.) but named only thirty-five years later by Dr. Eleming. lire's figure 

 is not, however, very correct, for it does not represent the incurvature of the 

 beak which is always present, nor is the area ever as wide as is there depicted. 

 Sp. Urii has received several other names, for it is highly probable (if not per- 

 fectly certaia) that the Sp. Clamyana, King,* from the Permian formation, and 



* The re-occm'rence of several carboniferous species in the Permian strata appears to be 

 ahnost certain, although such has been doubted by several palaeontologists. It is therefore 

 probable that the following carboniferous (C), and Permian (P) shells are identical, notwith- 

 standing that they have received distinct specific names according to the strata in which they 

 have been discovered. Thus Terehratula sacculus, C, = Sp. sufflata,V;? Spirifera Urii, 

 C, = Sp. Clannyana, P; Spiriferina octoplicata, C, = Sp. cristata, P. ; Camarophoriaerumejia, C, 

 = Ca. Schlotheimi, P. ; Ca. glohulina. P., = Ca. rhomhoidea, P. ; and the Liiigula Credneri, P., have 

 been found in the carboniferous strata hj Mr. Kirkby. The re-occurrence of species is a subject 

 that has been too often supposed impossible, and treated accordingly. 



