
Gdl 
Gd 
FC 
Gd4 
Gd 
Gdl 


WENLOCK GROUP. 

a 
Reference to McCoy’s 
Synopsis: and Figures of Genera. 
Names and References; Observations, &c. 
143 
Numbers and Localities, 

Spirigerina, p. 198. 
Spirigerina, p. 197. 
var. of S. marginalis, p. 197. 
Hemithyris, p. 201. 

Hemithyris, p. 205. 


Atrypa reticularis, Linn. (Anomia reticularis, 
Syst. Nature, 12th ed. Siluria, 2nd ed. pl. 
21, figs. 12, 13, Davidson, 1. c. t. 14), 
Strong lamellar fringes roughen the whole 
shell and double its bulk, but these are 
rarely preserved, except in shale, being of 
course entangled in the matrix. 
Atrypa marginalis, Dalm. (Siluria, 2nd ed. 
pl. 22, fig. 19, in pt., Davidson, 1]. c. t. 15, 
figs. 1, 2). Almost as common as the last 
in Silurian rocks, and ranging down to 
Middle Bala, but never rising above Silu- 
rian. The defined sinus in the front, and 
the moderately narrow striz, distinguish it 
from the next form. 
Atrypa imbricata, Sow. (Sil. Syst.) Siluria, 
2nd ed. pl. 22, fig. 19, in pt. Davidson, 
Sil. Brach. t. 15, figs. 83—8. Coarse and 
few ribs, and the want of a defined medial 
sinus, and the rough imbrication, are cha- 
racters. 
Atrypa? Grayii, Davidson (Sil. Brach. p. 141, 
t. 13, figs. 14—22, Rhynchonella, Siluria, 
2nd ed. Foss. 57, fig. 3). 
Athyris? depressa, Sow. (Davidson, Sil. Brach. 
t. 13, fig. 6). 
Athyris? compressa, Sow. (Siluria, 2nd ed. 
pl. 22, fig. 22). 
Nucleospira, Hall. Spiral calcified arms, and 
a minute area in either valve, and a smooth 
surface, mark this obscure genus. 
Nucleospira pisum, Sow. (Spirifer? Sil. Syst. 
and Siluria, 2nd ed. pl. 21, fig. 7, Davidson, 
Sil. Brach. t. 10, figs. 16—20). 

a. 777, ventral valve in- 
terior; a. 778, dorsal valve 
interior; a. 780, Dudley, 
F. C.; b. 756, Wenlock ; 
b. 757, Sedgley ; Myddle- 
ton Park (Wenlock Shale), 
Caermarthen; b. 760, Coed 
Sion, Llangadoc (W. Shale); 
b. 761, Keepers Lodge, 
Golden Grove (W. Shale). 
b. 762, Dudley, F.C. ; b. 
760, Wenlock. 
a. 774, large and fine; a. 
775, young variety; a. 776, 
very few ribs, Dudley, F. C. 
a. 651, a.652, Walsall, Dud- 
ley, F.C. 
Dudley. 
Dudley. 
b. 764, Dudley, F.C.; b. 
765, Wenlock. 
