DAVIDSON 
■ — SCOTTISH CARBONIFEROUS IIUACIIIOPODA 
99 
geologist or not, will quit the latter valley without visiting the 
castlc-city of Caerphilly, with its leaning tower, the most stu- 
pendous ruin in South Wales, which we are told contained within 
its walls, at the time of the memorable siege in the reign of 
IWward II., " two thousand fat oxen, twelve thousand cows, twenty- 
five thousand calves, thirty-thousand sheep," as food for the 
garrison. 
THE CARBONIFEROUS SYSTEM IN SCOTLAND CHARAC- 
TERIZED BY ITS BRACHIOPODA. 
By TuoMAs Davidson, Esq., F.R.S., F.G.S., Hon. Member of 
the Geological Society of Glasgow, etc., etc. 
( Continued from Vot. Hi., p. 25. J 
Family Stropiiomenid^e. 
This family, which has been termed OdJiidm by some authors, coniprises 
several genera and subgenera, of ■which Strophomena, Streptorhi/ncJms, and 
Orthis alone have been found represented in Scottish Carboniferous strata. 
Genus Okthis. Dalman. 1827. 
The genus Orthis forms a vrell characterized group, especially specifically 
numerous and abundant in the Silinian and Devonian systems, is considerably 
reduced during the Carboniferous period to appear no longer (?) in subsequent 
stages. Two species alone have been hitherto discovered in the Carboniferous 
rocks of Scotland. 
XXII. — Orthis resupinata. Martin. PI. i., fig. 11-15. 
Conchyliolithus anomites resupinatus. Martin, Petrif. Derb., pi. xHx, figs. 13- 
14, 1809. Terehratula resupinata, Sowerby Min. Con., tab. 325. 
In shape it is either transversely oval, or elliptical, but vaiying greatly in 
the convexity of its valves ; some examples are moderately convex, others gib- 
bous, hence the specific denominations of resupinata, connivens, and gibtiera, 
which have been applied to what we must look upon as variations of a single 
species. The liinge-line is straight and shorter than the greatest wdth of the 
shell, with rounded cardinal angles ; each valve possesses a small area, of 
wliich tlie ventral one is the largest, and divided in its middle by an open 
triangular fissure. The dorsal valve is always the deepest, and either regidarly 
and evenly convex or slightly flattened from the middle to the front. The 
ventral valve is slightly or moderately convex at the rostral portion, but be- 
comes flattened, or even, sometimes slightly concave as it approaches the sides 
.or frontal margin. The beak is small, slightly promiaent and iiieui-ved. Ex- 
teriorly the surface is closely covered with fine thread-Uke rounded radiating 
