MYALINA. 
45 
Bemarhs. — These fossils clearly belong to the German species described as 
Hoplomytilus crassus by Sandberger. They are all fragmentary, consisting only 
of the umbonal portions of the shell, so that its general shape is unknown. The 
same is the case with the specimens figured by Sandberger, and his description 
does not throw any further light on the subject. The reason of this appears to 
be the extreme tenuity of the lower part of the shell. 
Under the umbo, on the anterior side, there appears to be a narrow gap 
between the two margins, which was probably the aperture for a byssus. 
From Sandberger' s figures the shell appears to have been very deep. 
Affinities. — Myalina luna seems very similar in the general contour of its 
upper part, and I once thought it might be identical. As far as can be judged, 
however, it is a much flatter shell, its umbo is not actually pointed, it has a 
very small convex anterior wing, and its anterior side seems to sink to the 
margins with a simple steep slope instead of being doubly angulated as in the 
present species. 
Myalina (olim Pterinea) Goldfussiana, de Koninck,^ from the Carboniferous, 
presents some points of likeness, but is distinguished by its very different contour. 
2. Genus. — Myalina, de KonincJc, 1842. 
This genus contains mytiliform, subequivalve shells, which are generally 
higher than long. The umbones are arched, sharp, terminal, and anterior. The 
hinge is thick, large, and long, and bears several longitudinal cartilage-grooves. 
There are two muscular impressions ; the pallial line is simple, and there is no 
byssal notch. The supero-posterior region seems to be frequently produced and 
flattened, so as to form an indistinct rudimentary wing. It is common in the 
Carboniferous and Permian, and appears to extend from the Silurian to the Trias. 
1. Myalina egeegia, n. sp. PI. Ill, figs. 4, 4 a, 5. 
Description. — Valves large, short, very broad, flatfish, slightly inequivalve. 
Umbo small, depressed, proximate, situate at the extreme anterior point, and 
arching forward so as to project laterally beyond the rest of the shell, but not to 
overhang the hinge-margin. Hinge-margin long (giving the greatest length of 
^ 1842-4, de Koninck, ' Descr. Anim. Foss.,' p. 126, pi. iii, figs. 7 a, b. 
