MIDDLE BALA GROUP. 

59 







Column Sb ncaree ot aaah Names and References; Observations, &c. Numbers and Localities. 
Gl Pl. 1 4, figs. 41, 42, p. 223. | Orthis, sp. near to O. porcata. Mynydd-y-gaer, Llanefydd. 
Gl p. 216. Orthis elegantula, Dalm. (Siluria, 2nd ed. pl. | Everywhere in the Bala 
5, fig. 5). The weed of the Silurian and | rocks; in Caernarvonshire 
Upper Cambrian rocks; appearing under | at Pwllheli; Snowdon; 
many varieties in Britain and Sweden; ap- | Moel Hebog, &e. Allround 
parently unknown in 8. Europe. | Bala Lake in Merioneth- 
shire. The Berwyns, east 
side (Milltir Cerrig), Welch- 
pool; Meifod; Moel Uch- 
las near Llanfyllin; Hor- 
derley; Acton Scott; and 
all the Caradoe district. 
Gl p- 221. | Orthis parva, Pander. Considered a distinct | Dinas Mowddwy; Llansant- 
species by De Verneuil and McCoy, and | fraid, Glyn Ceiriog; Bryn 
others. I think it only a sharply ribbed | Melyn, Bala; Yspytty Evan. 
variety of O. elegantula, with which it is | Moel Uchlas, &e. 
generally intermixed. Ardwell, Girvan, Ayrshire, 
Gl p: 221. | Orthis parva, var. avellana, De Verneuil. Geol. | b. 217, N. of Tremadoc ; 
Russ. t. 13, figs. 3, 4. Tan-y-Bwlch-y-groes. 
G Spirvfera, p. 192. Orthis biforata, Schloth. (Davidson, Mon. Brach. 
| Pal. Soc. Introd. pl. 8, fig. 146). One of the 
| commonest of the Bala types, ranging from 
Lower Bala to Wenlock rocks. It looks 
| like a Spirifer, and was so named by Prof. 
| McCoy, as it had been by other authors. 
There are no internal shelly spires. It is 
easily divisible into — | 
G p. 192. | Orthis biforata, proper, with 6 to 9 ribs on the | b. 239*, Troutbeck ; b. 239, 
raised front. Bryn Melyn, Bala. 
G Spirifera, p. 192. Orthis biforata, var. a Lynx (Spirifer, Kichwald | a, 145, Meifod; Llanfyllin; 
&e.), 4 ribs on the fold. | Bala; Glyn Diffwys, Cor- 
wen; High Haume, Dal- 
ton; &e. 
G p- 192. Orthis biforata, var. 8 dentatus. Coniston; Rhiwargor; Llan- 
| wddyn; Cyrn -y - Brain, 
| Wrexham ; Coniston; Ra- 
| venstonedale. 
Gl Spirifera, p. 198. Orthis fissicostata, seems quite distinct. b. 235, Tyn-y-Cabled;b. 236, 
Orthis (0. biforata, var. fissicostatus), McCoy. 


Alt-yr-Anker; b. 257, Pen- 
arth, Meifod; Ravenstone- 
dale. 
8—2 
