150 Mr. I". Chapman on some 
by the middle lobe ; posterior angle full and evenly rounded, 
anterior rounded and narrowed off. Middle of valve with a 
short, low, transverse, clavate ridge or swelling, which pro- 
jects a little beyond the dorsal margin. ‘Towards the ends 
of the valves the sides are swollen, especially near the poste- 
rior extremity, and represent incipient lobes. Surface of 
valves delicately pitted. Edge view of carapace elongate- 
oval, with rounded ends. Length *44 millim.; height *266 
millim. 
This species is nearly allied to Beyrichia (? Kledenia) 
plagosa, Jones *, which was obtained from strata of Wenlock 
age at Beechey Island, Canada. It differs, however, in the 
position and shape of the central lobe, which in our specimen 
is more pronounced and projects beyond the margin; and, 
further, the surface ornamentation in A. gotlandica is an even 
and delicate pitting. 
Botuia, Jones & Holl [1886]. 
Bollia auricularis, Jones. 
Bollia auricularis, Jones, 1887, Ann. & Mag. Nat. Hist. ser. 5, vol. xix. 
p. 408, pl. xiii. figs. 10 a-e. 
This species is uot uncommon in the Gotland washings, 
and the measurements of the valves agree very closely with 
those of the originally described specimens from Ironbridge, 
Severn. 
Silurian; Mulde, Gotland. 
Bryricuia, M‘Coy [1846]. 
Beyrichia concinna, Jones & Holl. 
Beyrichia concinna, Jones & Holl, 1886, Ann, & Mag. Nat. Hist. ser. 6, 
vol, xvii. p. 356, pl. xii. figs. 22 a, b. 
The Gotland specimens measure about one third more than 
the specimen figured by Jones and Holl from the Silurian of 
Dormington, but otherwise they possess the same charac- 
teristics. 
Silurian; Mulde, Gotland. Common. 
Beyrichia muldensis, sp. n. (Pl. III. fig. 10.) 
Valve oblong, ventral margin slightly convex, ends nearly 
equally rounded, and with a marginal raised rim round the 
ends and the elliptically curved ventral border. Surface of 
* Ann. & Mag. Nat. Hist, ser. 3, vol. i. 1858, p. 248, pl. ix. fig. 2. 
