DAVIDSON — SCOTTISH CARBONIFEROUS lilUCIIIOPODA 
21 
Hpirifenna cridalu var. octojdicata, and Sp. insmljda are tlic only two species 
belonging to this snb-genus that have been hitherto discovered in our Scottish 
carboniferous rocks. 
XVII. — Spieiferina ceistata, var. octoplicata. J. de C. Sowcrby. 
Plate xii., figs. 3G-38. 
Spirifer odoplicatus, Sowcrby, Min. Con., p. 120, pi. 562, figs. 2, 3, 4: 1827. 
Spiriferina cristatay ax. octoplicata, Dav. Mon. Garb., p. 38, pi. vii., figs. 37-47. 
In external shape this shell is more often transversely sub-rhoniboidal, witii 
nearly equally convex valves, the hinge-line being eitiier as long or rather 
shorter tliau the greatest width of the shell, with acute or rounded cardinal 
angles ; tlie area is triangular, slightly concave, and of variable width. In the 
dorsal valve the mesial fold is usually composed of a single rib, wMch is often 
flattened along the middle ; but in some rare examples there exists a rudimen- 
tary one on either of its slopes, so that in some instances the fold assumes to- 
wards the front an obscurely bipHcated, or triplicated appearance. In the 
ventral valve the sinus is deep and acute, wliile both valves ai-e ornamented 
with from eight to twelve angular ribs, which are (as well as the sinus and 
fold) closely covered with numerous small granular (spinose) asperities, wliich 
give to the slieli a rough feel and appearance. The sheU-structure is also per- 
forated by minute tubuli, of which the external orifices may be readily detected 
by the aid of a common lens. In the interior of the ventral valve a sharp 
mesial septum rises from the bottom of the valve, and partly divides the spiral 
cones. The species we are at present describing varies much in general shape, 
as well as by the number of its ribs ; it is never a large shell, although some 
English specimens have been found more than double the size of any Scottish 
one that has come under my observation, none of these last having exceeded 
some six lines in length by about seven in breadth. 1 am also still inclined to 
maintain the opinion expressed in my monograph, namely that the shell under 
description bears so close a resemblance to the Permian Sp. cristata of Schlo- 
theim that it cannot be specifically separated, and could not in any case claim 
more than a varietid. cUstuiction. 
Sp. octoplicata has been fomid at Gare, in Lanarkshire, at two hundred and 
thirty-nine fathoms below the " EU coal at Braidwood GUI, three hundi'cd ; 
at HaUcraig Bridge, three hundred ; and at Raes three hundred and forty-one 
fathoms. The shell lias also been collected in the same county at Brockley, 
near Lesmahago ; Auchtentibber and Calderside, High Blantyi-e ; Capcl Big, 
East Kilbride ; Strathavon ; and Bobroyston, north of Glasgow. In Ben- 
frewshire, at Arden- and Orchard-quai'ries, Thornliebank ; in Stirlingshire, 
in the Corrie Bui-n beds ; in Ayrshu-e, at Boughwood and West Broadstonc, 
Bcith ; Auchenskeigh, near Dairy ; HaUerliii'st, Stevenston ; Craigis, near 
Kilmarnock ; and Meadowfoot, near Drumelog. It has also been found in 
West Lothian, as weU as in the Island of Ai-ran.* 
* Sp. cristata var. octoplicata is a common shell in the lower red carboniferous sandstone of 
Kilth'ess ; in Ireland Sp. partita of Portlock being a sjnonym. 
Since the publication of the first pages of my paper in the December number of the 
" Geologist," Mr. Kelly lias infoiTued me that the quotation at p. 465 relative to the arrange- 
ment of the Carboniferous system in Ireland does not represent his views, and he has kindly 
furnished me with the following note. 
" My subdivisions are, 1, Old Red Sandstone ; 2, calciferous-slate ; 3, limestone ; 4, coal 
measures. The Kildress red and yellow sandstone, which is one, is not lower coal-measures ; 
it hes" (as I have stated) "below the calciferous-slate. Again, the Old Red Sandstone is not 
that which predominates. This rock averages about one thousand feet thick in Ireland, and 
is not much exposed, being covered with limestone. Our calciferous slate is considerable in 
thickness, and in the best developed places (Olonea, near Dimgarvan) is half of it made up of 
thin bands of limestone, the other half calcareous shale. The fossils in both insepai'able, so 
that the calciferous slate and mountain-limestone might be considered as one division, but it 
