— [fT 
Case and 
Column of 
Drawers. 
FC 
Gd2 
Gd 
Gc8 
Reference to McCoy's 
Synopsis: and Figures of Genera. 

O. parva, p. 221. 
Spirifera, p. 192. 


WENLOCK GROUP. 

145 

Names and References; Observations, &c. 
a a 
Numbers and Localities. 

Orthis elegantula, Dalm. (Siluria, 2nd ed. pl. 
20, fig. 12. Davidson, Sil. Brach. t. 27, 
figs. 1—9). Not so common in the Dudley 
limestone as in the Bala rocks, but still very 
frequent. I think O. parva a mere variety, 
and feel inclined to keep O. orbicularis 
distinct. 
Orthis, var. small and triangular. 
Orthis orbicularis, Sow. (Siluria, 2nd ed. pl. 
20, fig. 9). A much rounder and less tri- 
angular shell than O. elegantula, but still 
very closely allied. It is far more common 
in Ludlow rocks (as at Sedgley), but here 
and there occurs in true Wenlock; as at 
Benthall Edge. 
Orthis hybrida, Sow. (Siluria, 2nd ed. pl. 20, 
fig. 13. Davidson, Sil. Brach. p. 214). 
Orthis Lewisii, Davidson (Bull. Soc. Géol. Fr. 
2nd. ser. Vol. v. t. 3, fig. 19, Sil. Brach. t. 26, 
fig. 4). 
[Orthis porcata, McCoy (see p. 89), is found, 
though rarely, in the Dudley limestone. ] 
Orthis Bouchardi, Davidson (London Geol. 
Journ. pl. 13, figs. 5—8; Bull. Soc. Géol. Fr. 
Vol. v. pl. 3, fig. 19). 
Orthis biforata, Schloth (De Vern. Geol. Russ. 
t. 3, Davids., l.c. Introduction, pl. 8, fig. 146). 
Rare in Wenlock rocks: common in Cam- 
brian rocks:—this’ species lingers on, to 
shew among many others how much closer 
the relations are between the Upper Cam- 
brian and the true Silurian strata, than 
between the former and the lower Cam- 
brian. 
Orthis equivalvis, Davidson (Sil. Brach. t. 30, 
figs, 9, 10; Siluria, 2nd ed. p. 251). 


a. 753, interior ventral 
valve; a. 752, interior dor- 
sal valve; a. 754, mere tri- 
gonal variety, Dudley, F.C.; 
b. 769, Erw Gilfach, Builth; 
a. 785 (as O. turgida), Coed 
Sion, Llangadoc, W. Shale. 
a. 892, a. 893, a. 894, Fal- 
field, Tortworth (Earl Du- 
cle). 
b. 770, Dudley, F.C.; b. 
771, Whitfield, Tortworth 
(Earl Ducie). 
a. 659, Dudley, F. C. 
b. 748, b. 772, Dudley, F.C. 
b. 773, Dudley, F.C. 
b. 774, Walsall, W. Shale. 
19 
