LAMELLIBRANCHIATA.] UPPER PALAOZOIC MOLLUSCA. 491 
A'l the specimens, both British and foreign, which I have examined, agree rather with the figures of Gold- 
fuss than of King, in haying the cardinal area scarcely more than the third of a line wide, and nearly parallel- 
sided. 
Position and Locality—Common in the Permian limestone of Humbleton. 
BAKEWELLIA INFLATA (Brown Sp.) 
Ref. and Syn, = Avicula inflata + A. discors + A. Binneyi Brown, Manchester Geol. Trans. Vol. I. t. 6. f. 25 
to 28; = Bakewellia antiqua (not of Minster) King, Perm. Foss, t. 14. f. 28 to 34. + B. tumida id. id. 
t. 14. f. 35 to 37. 
Desc.—Obtusely trigonal, diagonally gibbous ; beaks large, tumid, projecting beyond the hinge; posterior 
wing slightly pointed, extending as far as the posterior end, gradually sloped from the body of the shell, without 
being abruptly flattened or defined ; posterior margin very slightly sinuate ; anterior lobe obtusely rounded, tumid, 
scarcely defined from the body of the shell by a very obscure, shallow, byssal sinus ; surface marked with slightly 
imbricating, concentric lines of growth ; cardinal area in each valve rather wide, triangular, with about two earti- 
lage pits in front, and three behind the beak. Average length from beak to respiratory margin five lines, in 
60 
proportion thereto length of hinge-line from anterior to posterior end {%,, length of posterior wing from beak ©, 
width of body at right angles to posterior slope 4, width of posterior wing ,%, depth of left valve ~, width of 
both cardinal arez ~?. 
The main differences between this species and the B. ceratophaga are the greater width, obtuseness, and 
tumidity of the present species, and the posterior wing not being abruptly flattened or defined, and being less 
deeply sinuated in the posterior margin, the anterior lobe also being more broadly rounded, and the byssal sinus 
comparatively obscure. It is quite possible, however, that they may be varieties of one species, as the strength 
of the byssal sinus varies very materially even in different parts of the same specimen; meanwhile, as it is easily 
recognised, I keep it distinct for the present, but place it under Capt. Brown’s earliest British name, as I find, 
from authentic specimens in Count Miinster’s collection, that his Avicula antiqua is perfectly identical in all 
respects with the internal casts of the A. ceratophaga in its most typical form, some of the specimens even 
shewing the sculpturing of the surface of the latter species, though under the former name. Neither from 
the figures nor description, nor the examination of authentic specimens, can I find any grounds for the spe- 
cific separation of King’s Bakewellia tumida; the depth even by his own admission being subject to great 
variation ; but authentic specimens shew no approach to the great depth, apparently represented in his figure, 
of the cardinal area, I have very indistinctly seen the cartilage pits. In the Manchester specimens the cavity 
of the beak shews two or three small accessory muscular impressions ; but the cast of the wide area between 
the beaks shews neither the cartilage pits nor hinge-teeth, so I must suppose that Prof. King had better 
specimens. 
Position and Locality.—Common in the Magnesian limestone of Humbleton (often nine lines long); very 
common, but very small (varying from one to four lines long) in the red Permian marls near Manchester, 
Genus. MYALINA (de Koninck). 
Gen. Char.—Very inequivalve*, obliquely trigonal, diagonally tumid; beaks anterior, terminal; a slight 
sinus in the anterior part of the ventral margin for the byssus; anterior side obsolete; posterior end wide, 
obliquely truncate or rounded; hinge-line of moderate length, erect, simple; cartilage facets within it usually 
striated lengthways, inclining outwards, bounded by an internal ridge running along and a little below the hinge- 
* M. de Koninck says equivalve, but I entirely concur with Prof. King in supposing that they will all be found to 
be inequivalye when perfect specimens, such as we have seen, are examined, 
