298 F. R. Cowper Reed—Fossils from Dufton Shales. 
by 8-9 simple subangular straight ribs on each side, decreasing in 
strength towards lateral angles, and equal to or rather narrower than 
the subangular interspaces, which occasionally show a fine central 
line down them. In a few cases a small secondary rib arises close 
to the margin on the flank of a primary rib on either valve, but it 
is always short and inconspicuous. Surface of valves covered with 
coarse puncte (showing as sharp pustules on an impression of the outer 
surface) arranged with some regularity in concentric and radial rows. 
mm. 
Dimensions. Length : 5 5:5 
Width : 5 8-0 
Remarks.—This little shell is much like some species of Scenidium, 
the character of the ribbing and punctation, as well as the shape of 
the shell, recalling members of this genus. We may especially compare 
Se. elandicum, Wiman,’ from the West Baltic Leptena Limestone. 
The non-formation of a spondylium in the brachial valve is, however, 
an important difference, but Hall & Clarke* have pointed out that 
there are transitional forms between Orthis and Scenidiwm, and probably 
this species is such. It cannot be regarded as the young or a variety 
of O. actoniea, Sow., the details of the ribbing and punctation, as well 
as the internal characters, being distinctive. 
Postscript. Since the May number of the Grotoercan Maeazine 
was issued Dr. Marr has pointed out to me that there is some doubt 
as to whether the beds from which the above-described fossils were 
obtained are strictly referable to the Dufton Shales in the recent 
and restricted use of the term. Lithologically the rock resembles 
the Corona Beds and contains Lingula tenuigranulata. However, 
Professors Harkness and Nicholson employed the name Dufton Shales 
in a wide sense, including in them the Corona and other beds, and it 
is with this earlier and broader application that the term must be here 
understood. It is unfortunate when the same term has thus been 
used with two different meanings, particularly as it results from an 
alteration of its original significance. 
EXPLANATION OF PLATES XXIII AND XXIV. 
Brame XOxUET: 
1. Crisinella Wimani, sp. nov. Zoarium. x 3. 
2. Ditto. Celluliferous side of branch. <x 10. 
3. Ditto. Reverse side of branch. x 10. 
4, Orthis melmerbiensis, sp. nov. Internal cast of pedicle-valve. x 5. 
4a. Ditto. Anterior marginal view of same specimen. x 5. 
4b. Ditto. Portion of surface of same valve. x 12. 
5. Ditto. Internal cast of pedicle-valve. x 4. 
6. Ditto. Ditto. x 5. 
7. Ditto. Wax squeeze of pedicle-valve, showing ribbing. x 6. 
8. Ditto. Internal cast of brachial valve. x 4. 
PLATE XXIV. 
1. Orthis (Scenidium ?) equivocalis, sp. noy. Impression of brachial valve. «x 5. 
2. Ditto. Internal cast of same brachial valve. x 5. 
3. Ditto. Impression of pedicle-valve. x 4. 
‘ Wiman, Arkiv f. Zool. (Stockholm), 1907, Bd. iii, No. 24, p. 7, t.i, figs. 5-11 
2 Hall & Clarke, Paleont. N.Y., vol. viii, Brach. i, p. 241. 
