
Case and 




Gelato Reference to McCoy's 
Drawers. Synopsis : and Figures of Genera. 
Gl p- 228. 
Gl Pl. 18, figs. 20—24, p. 229. 
Gl p- 2380 
Gm 
Gm 
p. 231. 
Gm Pl. 1 8, fig. 29, p. 232. 
Gm | Leptena (McCoy does not 
admit Strophomena). 
Gm Leptena, p. 241. 


MIDDLE BALA GROUP. 

Names and References; Observations, &c. 

Orthis testudinaria, Dalman (Siluria, 2nd ed. 
pl. 5, figs. 1—2). A much coarser striated 
shell than the O. elegantula, and with dif- 
ferent hinge-characters, else not unlike that 
species, 0. testudinaria is however wholly 
a Bala rock fossil. 
Orthis turgida, McCoy. One of the most con- 
vex of species. It is a very rare one. The 
space between the great muscles of the 
dorsal valve usually occupied by a low ridge 
is here a sharp one. 
Orthis Vespertilio, Sow. (Siluria, 2nd ed. pl. 6, 
figs. 1—3). <A local British species—so 
strongly divided into two convex lobes, that 
it was originally called bilobata by Sowerby. 
The dorsal valve has a sharp keel all 
down it. 
Orthisina. Distinguished from Orthis no less 
by the very large area and covered delti- 
dium, than by the peculiar shape of the 
teeth in the smaller valve. 
Orthisina adscendens, Pander (Geol. Russ. Vol. 
IL. p. 203, pl. 12, fig. 3). Striated roughly 
and with decussating striz of growth. 
Orthisina scotica, McCoy. Ribbed strongly 
in a radiate fashion. 
Strophomena, Ratinesque. Flattened shells ex- 
panded, not convex as Orthis; one valve 
frequently concave—the other convex. And 
the large central tooth or cardinal process 
double. 
Strophomena antiquata, Sow. (Siluria, 2nd ed. 
pl. 20, fig. 18). A very unusual form of this 
genus, for it is covered with thick blunt ribs 
and ridges. The species ranges up into the 
Ludlow rocks. 



61 
Numbers and Localities. 
All through the sandy 
part of the Bala series 
abundant; Alt-yr-Anker, 
Meifod; Pwllheli;the Hol- 
lies; b, 225, Blaen-y-ewm ; 
Llansantfraid; Glyn Cei- 
riog; a. 148, Horderley. 
a. 181, N. of Conway. 
b. 252, Blaen - y - cwm, 
Nantyr; Bala; Llangollen; 
Meifod ; Welchpool; Bwlch- 
y-ciban, Montgomeryshire ; 
Horderley; Coniston; Roth- 
er Bridge. 
b. 258, Cyrn - y - Brain, 
Wrexham. Llansantfraid, 
Glyn Ceiriog; a. 142, Cefn 
Coedog. 
a. 143, Craig Head, Gir- 
van; one specimen, b. 260, 
said to be from Colmonel, 
i.e. Lower Bala. 
Range, Upper Cambrian, 
i.e. Lower Bala, and Are- 
nig rocks. Devonian. 
b. 254, Coniston, Bala: 
Llangollen; b. 253, Blaen- 
y-cwm Nantyr; Llansant- 
fraid. 
