MODIOLOPSIS. 
43 
has a more convex and less oblique inferior margin, and is mucli more rounded 
over the median keel. 
In Myalina Bodana, F. A. Romer,^ the anterior side is more produced, the line 
of greatest elevation less pronounced, and the upper and lower margins more 
arched. 
Mytilus antiquus, Goldfuss,^ is decidedly more angulated, and has a larger and 
more convex anterior lobe. 
Goniophora trapezoidalis, Kayser,^ is narrower behind, has a stronger and 
sharper keel, a more produced and convex anterior margin, and a much less 
distinct anterior depression. 
Modiomorpha submissa, Barrande,* as given by Barrois,^ is very similar in 
contour, but is very much less transverse ; as given by Barrande it differs more 
widely. 
3. MoDiOLOPSis, sp. PI. IV, fig. 7. 
Bemarhs. — In Mr. Vicary's Collection is a specimen of the posterior part of ^ 
the left valve of a shell which is too defective for description, but which does not 
belong to any of the associated species. It is rather large, flattish, and decidedly 
transverse. These are signs of a rounded oblique keel, or line of greatest 
elevation, which vanishes before it reaches the margin. The posterior margin 
is oblique and slightly convex, the postero-inferior corner rapidly rounded, and 
the inferior margin oblique. The surface is ornamented by a few abrupt, steep, 
step-like ridges, between each of which are seven or eight fine rounded threads or 
growth -strise. 
It seems somewhat similar in shape and ornament to Modiomorpha submissa, 
Barrois," and to some of the species of Modiolopsis described by Barrande, and for 
that reason I have placed it provisionally in the present genus. It appears to be 
a less transverse shell than Modiolopsis polita. 
Locality. — Wolborough. 
' 1860, F. A. Edmer, ' Beitr.,' pt. 4, p. 162, pi. xxv, figs. 11 a, b. 
2 1834-40, G-oldfusa, ' Petref. Germ.,' vol. ii, p. 173, pi. cxxx, fig. 5. 
2 1885, Kayser, ' Jahrb. Konig. Preuss. GeoL Landes.,' 1884, p. 19, pi. ii, fig. 4. 
^ 1881, Barrande, ' Syst. Sil. Boheme,' vol. vi, pi. cclviii, figs. 4, i-7, Et. F. 
^ 1889, Barrois, ' Faun. Calc. d'Erbray,' p. 176, pi. xii, figs. 2 a—c. 
6 1889, ibid. 
