138 DEVONIAN FAUNA. 
by Schnur ;' the chief differences being that the fold is less arched, and that its 
sides are much less sharply divided from its wings. Rémer’s original shell is 
further distinguished by its sharper and more irregular ribs. 
The marginal expansions seen in some Lummaton specimens and in Barrande’s 
figures emphasize its strong resemblance to Camarophoria crumena, Martin, sp.” 
I cannot agree with Clarke and Kayser that C. ascendens is identical with 
C. protracta, Sowerby, sp., though no doubt they are akin. Sowerby’s shell, if I 
understand Davidson rightly, is much more elongate, has a longer beak and 
deeper ventral valve, and differs in some other particulars. 
Rh. Ferquensis, Gosselet,*® seems to differ in having sharper ribs, which extend 
to the umbones. 
CamanopHoria ascenpEns, Steininger, sp. (Young form). 
Description—Shell small, circular, lenticular. Dorsal valve shghtly convex, 
with a very broad, flat, and slightly elevated central fold. Ventral valve equally 
convex with the other valve, mesial sinus hardly perceptible, except at the margin. 
Margins meeting at an acute angle. Surface covered with numerous low, rounded, 
flat ribs, extending from the umbo and arching out laterally toward the margins. 
Beak elevated, incurved. 
Size.—Length, 10 mm.; width, 11 mm.; depth, 5 mm. 
Localities —There are fourteen specimens in my Collection from Lummaton. 
Remarks.—These small specimens have long puzzled me. They evidently are 
not related to either Rh. parallelepipeda or Kh. vmplewa. I questioned whether 
they might be a young form of Ith. cwhoides, but the more convex ventral valve, the 
loftier beak, and the more acute apical angle, beside one or two other points, 
make it clear that they could not belong to that species. When we come 
to Rh. subcuboides, however, we find most of these distinctions disappear, the 
chief differences remaining being the flatness of the shell and the small develop- 
ment of the mesial fold and sinus. I find that there are some specimens in both 
groups where these distinctions are less marked, and therefore I have little 
hesitation in regarding them as identical. 
At the same time, as the relationship is not apparent at first sight, I have 
thought it worth while to give a separate description of the present form, in case 
further evidence should arise to prove its distinctness. 
1 1854, Schnur, ‘ Paleontographica,’ vol. iii, p. 173, pl. xxii, figs. 3 a—d. 
2 1858, Davidson, ‘ Brit. Foss. Brach.,’ vol. ii, p. 113, pl. xxv, figs. 3—9. 
3 1887, Gosselet, ‘Ann. Soc. Géol. Nord,’ vol. xiv, p. 199, pl. i, figs. 1—9. 
