PAVIDSON — SCOTTISH CARIiONIKEROUS BRACIIIOPODA. 
19 
tliree liimdrcd and seventy-five fathoms below tlie " Ell coal ;" occurs also at 
Middleholm, near Lcsiiialiago and East Kilbride. In iStirlingsiiirc at Corric 
Burn and (Jainpsie niain-limestonc. lu llunlVewsliire at Orchard-quarry, near 
Tlioruliebank. In Ayrshire, at West Broadstone, Beith, and at Aucheuskeigh, 
near Dairy, etc. 
XIV. — Spirifera Carlukiensis. Davidson. PI. xii., fig. 29, 
Spirifera Carlukiensis, Dav. Men. 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 umbonc. Ventral valve convex, with a 
narrow mesial depression or furrow commencing at a short distance from the 
extremity of the Dcak and extending to the front, where it indents the margin 
of the opposite valve. The beak is small, pointed, and but slightly incurved ; 
the hinge-line much shorter than the greatest width of the shell, with its 
cardinal angles rounded, area small, triangular. This little shcU 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 Lanarksliire, at 
about three hundred and fifty-six fathoms below the " Ell coal," along with 
Sp. Urii, but it is a rare species, for in every hmidi-ed or more specimens of 
the last named shcU that is collected, a single example of Sp. Carlakioisis would 
occur. It has also been recently discovered near Strathavon in a bed of shale 
almost entirely composed of Sj). Urii, and is there nearly as rare as at Hill 
Head. 
XV. — Spirifera Urii. Fleming. PI. xii., fig. 30. 
Spirifer Urii, Fleming, British Animals, p. 376, 1828; Spirifera Urii, Dav. 
Mon. Carb., p. 58, pi. xii., figs. 13, li. 
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 liinge area ; it is nearly flat or slightly convex, especially at the um- 
bone, from whence a shallow mesial furrow extends to the front. The ventral 
valve is much deeper and more convex than the opposite 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, which are 
produced by the fraetui-e of the spines close to their bases. 
This abundant and interesting little species was noticed, and figured for the 
first time by Ure, in 1793, (History of liutherglen and East Kilbride, p. 313, 
fig. 12.) but named only tliirty-five years later by Dr. Elemiug. Ure's figui'e 
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 certain) that the Sp. Clannijam, King,* from the Permian formation, and 
* The re-occurrence of several carboniferous species in the Pei-mian strata appears to be 
almost certain, although such has been doubted by several palsenntologists. It is therefore 
probable that the following carboniferous (C), and Peimian (P) shells are identical, notwith- 
standing thaX they have received distinct specific names according to the sti'ata in which they 
have been discovered. Thus Terebrntida sacculm, C, = Sp. siifflj:in, P ;? Spirifera Urii, 
C, = Sp. Chiniit/ana, P; Spiriferina ocfoplicafa, C, = Sp.o'istata, P. ; Ciimarophnria crumetia^ C, 
= Ca. SiMofheimi, P. ; Ca. q/obiilina. P., = Ca. rhmnlmidea, P. ; and the Li/i</ii!a Creilneri, P., have 
been found in the carbouiferous strata by Mr. Kirkby. The re-occurrence of species is a subject 
that has been too often supposed impossible, and treated accordingly. 
