ANIMALS. 159 
cavity.. Dr. de Koninck has described a genus under the name of Myalina,’ which 
is perhaps the proper receptacle for these shells; but 1 am averse to placing them 
in it, in consequence of there being one or more Neocomian imeguivalved Mussels 
(e. g. Mytilus inequivalvis), and some recent species (JM. bilocularis, &c.) with umbonal 
transverse plates.* Perhaps there are some true Mussels in which the cartilage is 
exposed, and placed in a furrow, as in the two Permian species. The latter have 
the cartilage-plates or fulcra parallelly grooved as they are in Myalina (vide Pl. XIV, 
fig. 13). The Mytilus crassus, Fleming, belongs to De Koninck’s genus; and all the 
modioliform shells described by J. de C. Sowerby in Mr. J. Prestwich’s Memoir ‘ On 
the Geology of the Coal-field of Coalbrook Dale’ (vide Trans. Geol. Soc. Lond., 2d 
series, vol. v, P]. XX XIX, figs. 10, 15—18), appear to be congeneric species. As I 
strongly suspect these were all fresh- or brackish-water shells, one is seemingly 
warranted in characterising Myalina as a fresh-water genus. The next question for 
consideration is, whether it possessed any marine species. If the Permian forms 
belong to De Koninck’s genus,—WMyalina, like some other genera, may be said to 
contain both kinds, as they were undoubtedly oceanic shells. 
MytTiLus squamosus, J. de C. Sowerby. Plate XIV, figs. 1, 2, 3, 4, 5, 6, 7. 
CasTs OF BIVALVES RESEMBLING MUSCLES, Winch. Trans. Geol. Soc. Lond., vol. iv, 
p. 10, 1817. 
(2) Myryuus, N.S., Phillips. Phil. Mag., vol. iv, p. 403, 1828. 
— squamosus, J. de C. Sow. Trans. Geol. Soc. Lond., 2d series, vol. iii, p. 
120, 1829. 
_ == aN De la Beche, Geol. Man., p. 385, 1831; Germ. 
Transl., p. 459, 1832; 3d Eng. ed., p. 573, 
1833. 
— — ih Phillips, Encye. Met., vol. iv, p. 616, 1834. 
— — Pe Thomson, Outlines of Min. Geol. &c., vol. ii, 
p. 316, 1836. 
— Hausmanni, Goldfuss. Petrefacta, part ii, p. 168, pl. 138, fig. 4, 1837. 
— ACUMINATUS, J. de C. Sow. Phillips, Lardner’s Cyclop., Geology, vol. i, p. 
190, fig. 2, 1837. 
GERVILLIA, Geinitz, Leonhard u Bronn’s Neues Jahrbuch, p. 639, 1841. 
Myritus squamosvus, J. de C. Sow. Morris, Catalogue, p. 93, 1843. 
! The situation of the anterior adductor muscle is shown by the cast of the space intervening the 
horizontal plates (that is, the prolongation between the umbones in the cast represented in Plate XIV. fig. 5) 
displaying its impressions: these are seen on the prolongation; but they cannot be represented in the 
figure. Through an oversight, the impression marked c in fig. 7, Pl. XIV, is referred to the anterior adductor 
muscle in the explanation appended to the plate: it ought to have been named the impression of the anterior 
visceral or pedal muscle. 
® Description des Animaux fossiles, qui se trouvent dans le terrain carbonifére de Belgique, p. 125. 
8 The genus Drevssina, being a fresh-water group, is not taken into consideration. 
Kk Ke NY Ao 
