Genn^ oj" Loire r Ilt:l<Iei'h<:i'(/ OHtrneodd. — JL'/ch. 201 
base of anterior spine to point on posterior edge one-third of 
hight of valve beneath tlie dorsal line, the curve corresponding to 
something near a one-third segment of a circle. Posterior end 
most produced above, with a flattened border or flange projecting 
bej'ond the inner or contact edge ; flange widest above, vanishing 
in the lower third. Back strongly convex, without carina, l)ut 
with a shallow channel close to the edge. Surface smooth, valves 
tumid, with point of greatest thickness a little above the middle. 
In a view of the inner side the contact edges form an elongate- 
oval, with the anterior end sharply rounded or sub-acute, and the 
dorsal side straighter than the ventral. 
This species is too ol)viously distinct from the preceding to 
require comparisons. B. nratu has much wider valves, with 
({uite different surface contour: while B. rristiifa has the dorsal 
margin more convex, and a thin carina or crest on the dorsal 
slope. 
Firnaatioii (ind locality: Same as preceding. 
Type in Dr. C. E. Beecher's collection. 
Beechereila subtumida, var. intermedia, n. var. 
PLATE II, FIG. 15. 
Size of I'iglif cah:c: Length (excluding spine) about 1.17 mm. ; 
hight. 0.63 mm. 
This name is proposed provisionally for a single right valve, 
that, l)eing a little imperfect at the anterior end, I think it wisest 
to view with conservative judgment. At first I was inclined to 
regard it as a young right valve of B. iji-nta, l)ut on re-examination 
that view lost probabilit}', and I now believe that its relations are 
nearer B. suhhuaidn, with the chances strongly in favor of ultimate 
specific separation from both. A comparison of figs. 5 and 15 
shows that the latter is comparatively shorter, the antero-dorsal 
angle abruptly curved instead of gently declining, the anterior 
end probably blunter, and the ventral edge a little more convex. 
In the two points last mentioned the shape is more nearly as in Ji. 
oontd (see fig. 14) with which it agrees further in having the 
anterior spine less produced IjeyiMid the end of the valve, and its 
base situated farther back on the antero-dorsal slope — not however 
as much so as in that si)ecies. Its surface is less and more 
uniforml}' convex than B. unhfinnida, while B. ovafif has a low 
cardinal ridge running backward from the spine. :ind a shallow 
