10 
Mytilus septifer , n. sp. This species, a shorter and wider 
one than the last, is lobed in front like a Modiola, and fur¬ 
nished with a ridge that posteriorly bounds the anterior 
adductor muscular impressions. It occurs at Byers’ quarry, 
Whitburn, Roker, Suter point, and Marsden, in a formation 
probably equivalent to the German Rauchwacke. 
Edmondia Murchisoniana, n. sp. This species has a re¬ 
semblance to Sang, truncata, Goldf. It is inequilateral, rather 
tumid, and finely striated : with a rectilinear hinge line, and 
obtusely rounded terminations. Humbleton and Tunstall Hilfi 
Cardiomopha modiolifomis , n. sp. Pleurophorns id, King, 
cited in Geol. Russ. vol. I., p. 224. This species, in its mar¬ 
ginal outline, bears a resemblance to Mytilus Pallasi, de 
Yern., but it is a shorter, and a more tumid shell, and its 
umbones are more incurved : in the latter character, and in 
being diagonally tumid, it approximates to Cypricardia gla - 
brata, Phill. Old specimens occasionally become diagonally 
carinated like Cypricardia rhombea, Phill. Rare. 
Bakevellia, n. gen. This genus is proposed for some ine- 
quivalve shells hitherto placed in Avicula. It possessed two 
adductor muscles, and therefore has no relation to Avicula, 
which is a true Monomyarian : further, it is furnished with a 
plurality of cartilage pits (from two to five according to 
species), as in Perna and Gervillia; and it possesses anterior 
and posterior linear teeth similar to those of the Cuculloea- 
toothed Arks. Bakevellia appears to be related to Pterinea, 
but the latter has no cartilage pits. 
Bakevellia ceratophaga, Schl. Rather common. 
Bakevellia antiqua, Munster. Not so common as the last. 
Bakevellia tumida, n. sp. — Gervillia? id, King, cited in 
Geol. Russ., vol. I., p. 225. The umbones are much divari¬ 
cated, and the hinge plate, which is short, possesses generally 
five cartilage pits. Rather common. 
Bakevellia bicar inata, n. sp. Nearly smooth, winged, and 
furnished with two faint ridges on its anterior lobes. This 
may be a variety of B. antiqua. Tunstall Hill. 
Bakevellia Sedgwickiana, n. sp. Form somewhat acutely 
