MIDDLE BALA. GROUP. 
65 

Case and 
Column of 
Drawers. 

Gm 

Gm 

Reference to McCoy’s 
Synopsis: and Figures of Genera. 
Names and References: Observations, &c. 
Numbers and Localities. 


Pl. 1 1, figs. 1, 2, p. 261. 
— 
SS 
Ne 
ye o 
qe 
A ae 
lt yi 
ny 
LES 

Pl. 1 1, figs. 17, 18, p. 267. 
Avicula? p. 258. 
Pl. 11, fig. 16, p. 266. 
Pl. 1x, fig. 17, p. 272. 
Pl. 1K, figs. 7, 8, p. 273. 

Pl. 1 1, fig. 23, p. 275. 
Pterinea pleuroptera, Conrad ? 
Ambonychia costata, Conrad. 
Modiolopsis, McCoy. Confessedly a genus of 
convenience, it being extremely unlikely 
that Modiola-like shells, so different in ex- 
ternal characters from the living forms, 
should have possessed no internal charac- 
ters whereby to separate them. (The front 
muscular scars are deep and strongly de- 
fined, however.) Common in Bala rocks. 
Modiolopsis modiolaris, Conrad sp. 
Modiolopsis orbicularis, Sow. (Avicula, Sil. Sys- 
tem, t. 20, fig. 3, Siluria, 2nd ed. pl. 7, 
fig. 1). A very round and rather long than 
wide form, 
Modiolopsis inflata, McCoy. 
(AZ. antiquata of McCoy is a mistake. The 
species is Wenlock, and does not occur in 
Bala rocks.) 
Lyrodesma plana, McCoy. A genus with 
the characteristic numerous teeth of the 
Arcacide, but disposed fan fashion under 
the beak. 
Cleidophorus? ovalis, McCoy. Doubtfully re- 
ferable to this genus, which was proposed by 
Hall for toothless shells like flattened Cu- 
cullellee. 
Orthonotus, Conrad. A convenient group, 
| intended to enclose a number of Mytiloid 
shells, thin, without teeth; with a form like 
Myacites (but certainly with no relation to 
it), no pallial sinus, no wrinkled or granu- 
lated epidermis; and with dorsal and ante- 
rior lunettes. 

| 
| Orthonotus nasutus, Conrad sp. 
* 

a. 166*, Cyrn-y-Brain, 
Wrexham. 
Not in the collection. 
a. 160, Cader Dinmael. 
a. 160, Cader Dinmael. 
a. 160*, Horderley. 
a. 166, Acton Scott, Shrop- 
shire; and abundant in 
all sandy Bala rocks (rises 
into May Hill sandstone). 
J.W.S. 
a. 208, Pen-Cerrig, 
N. of Bala. 
Serth. 
a. 209, Yspytty Evan. 
a. 210, Dolydd Ceiriog 
waterfall, in the Berwyn 
Mountains. 
a, 211, Horderley. 
9 
