88 
Gustaf T. Troedsson 
II Description of (new) species. 
Brachiopoda. 
Oonotreta acuta n. sp. 
Pi. I, f. 3—4. 
The acute cone-shaped straight or slightly bent ventral valve is always com- 
pressed from two sides, mostly the posterior and anterior ones. The figured spe- 
cimen shows on each side a well marked groove, running from the beak to the 
margin. On other specimens more such grooves are observed. They may have 
been formed because of compression. On account af that the false area with its 
median furrow when developed has not been preserved. The surface is’ black and 
glossy, marked with fine concentric lines of growth, closer on the posterior than 
on the anterior side and sometimes crossed by very fine radiating lines. At the 
apex I have been unable to discern any foramen. The internal cast of the cir- 
cular dorsal valve (pi. I, fig. 4) is ornamented with a concentric striation and 
shows a well developed septum which occupies 2 / 3 or the whole of the length of 
the valve. On the posterior extremity of the septum and close to the margin there 
are two pairs of muscular scars the one behind the other. Both of them are small 
but distinct. 
The figured dorsal valve measures 0,86 mm. in length and 0,92 mm. in width 
the compressed ventral valve 2 mm. in height and — on the base of a flattened 
side — 1 or 1,26 mm. in width. 
The acute angle of the ventral valve and the fine ornamentation distinguish 
Conotreta acuta from other known species of the genus Conotreta Walcott. 
Discina (Orbiculoidea) radiata n. sp. 
Pi. I, f. 6—7. 
Shell almost circular in outline, a little longer than wide. The ventral valve 
slightly conical, the pedicle groove occupying one fourth or one third of the 
diameter. Apex is situated at about two fifths of the distance from the posterior 
margin. Dorsal valve more convex especially at apex near the margin. Surface 
glossy, marked with concentric unequal lines of growth, crossed by fine, radiating 
striae and more prominent thin wrinkles. Length 5 mm., height scarcely 1 mm. 
Plectambonites comitans Barr. 
Pi. I, f. 8—9. 
Of this species well preserved casts are found in the Staurocephalus zone and 
in the Brachiopod beds. They agree in every respect with a few of the figures of 
