42 
DEVONIAN FAUNA. 
umbones, its more convex and narrower anterior margin, its greater flatness, 
and its probably thin test. 
Modiolopsis modiolaris, Conrad,^ sp., of the Lower Silurian, is very similar in 
general shape, but has a still smaller umbo and a more attenuated front margin. 
Nuc'ula Krotensis, F. A. Romer,^ and 8anguinolaria amygdalina, F. A. E-omer,^ 
are much more regularly oval shells, and are narrower behind. 
Cardiomorplia alata, Sandberger,* is also in the same general style, but has a 
more produced and narrower anterior side, a straighter base, a less oblique 
posterior margin, and a much less marked diagonal angle. 
Sphenotus contractus, Hall,^ is also very similar in shape and in its anterior 
muscular impression, but is distinguished by a depression running across the valve 
to the inferior margin. 
2. Modiolopsis polita, Whidborne, sp. PI. IV, fig. 5. 
1889. Caediomoepha ? polita, Whidborne. Geol. Mag., dec. 3, vol. vi, p. 79. 
Description. — Left valve very long and narrow, convex, transversely scimitar- 
shaped. Umbo minute, depressed, proximate, situated almost at the anterior 
extremity. Hinge-margin nearly straight, about two-thirds the length of the 
shell. Anterior margin narrow, moderately convex. Inferior margin oblique and 
slightly concave. Infero-posterior corner much produced and roundly convex. 
Posterior margin obliquely convex. Line of greatest convexity running straightly 
down from umbo to infero-posterior corner, on each side of which the surface 
slopes almost flatly down. Front wing small, difiuse, and convex. Surface smooth. 
Shell -structure very thin. 
Size. — Length 45 mm., breadth 20 mm., depth of one valve 10 mm. 
Locality. — There is a single specimen of the left valve in the Torquay Museum 
in subcrystalline limestone, which may have come from Barton or Lummaton. 
Remarks. — This specimen, with the exception of one small portion, is a cast. 
It is distinguished by its great transverseness and its strong perpendicular 
anterior constriction. In general shape it bears a strong resemblance to some of 
the Mesozoic forms of Modiola. 
Affinities. — Modiola Kahlehurgensis, F. A. Romer,^ is less constricted anteriorly, 
1 1838, Conrad, 'Ann. Geol. Eep. N. Y.,' p. 118; and 1848, Hall, 'Pal. N. Y.,' vol. i, p. 294, 
pi. Ixxxi, figs. 1 a—g, and pi. Ixxxii, fig. 1. 
2 1850, F. A. Eomer, ' Beitr.,' pt. 1, p. 13, pi. iii, fig. 5. 
^ 18L>6, ibid., pt. 5, p. 6, pl. xxxiii, figs. 8 a, b. 
* 1853, JSaudberger, ' Verst. lihein. Nassau,' p. 234, pl. xxvii, figs. 4, 4 «, 4 b. 
5 1885, Hall, ' Pal. N. Y.,' vol. v, pt. 1, sect. 2, p. 284, pl. xxxix, fig. 15 ; and pl. xli, figs. 5—11. 
« 1855, F. A. R5mer, ' Beitr.,' pt. 3, p. 11, pl. vii, fig. 3. 
