O74, BRITISH PALASOZOIC FOSSILS. [ LAMELLIBRANCHIATA. 
be abundant everywhere in the green shales and arenaceous schists just over the black Utica slates so rich in 
Graptolites. 
Position and Locality—In the olive arenaceous schists of Keeper’s Lodge, Goldengrove, Llandeilo. 
Explanation of Figure.—Plate 1. K. fig. 9. Natural size, right valve. 
Genus. TELLINOMYA (fail). 
Gen. Char.—Kquivalve, inequilateral, compressed towards the margin, convex towards the beaks, without 
angular ridges ; beaks small, inconspicuous ; hinge without visible teeth or crenulations; muscular impressions 
two, near the dorsal margin ; shell very thin, closely laminated. 
TELLINOMYA LINGULICOMES (M‘Coy). Pl. 1. K. fig. 18. 
Ftef —ld. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VII. p. 56. 
Sp. Ch.—Obovate, slightly and evenly convex; beaks small, compressed, not prominent, close to the 
anterior end, which is broadly rounded; dorsal and ventral margins slightly convex, converging towards the 
narrow posterior end, which is truncated more or less obliquely, about two-thirds the width of the shell under 
the beaks, and has an almost imperceptible sinus between its inferior angle and the ventral margin; surface 
with fine, irregular, imbricating plicee of growth. Length one inch one line ; proportional width =. 
This is much allied to the 7. nasuta (Hall) of the Trenton group, but is smaller, shorter, and more regularly 
ovate. It has somewhat the form of Cardinia, with the delicate shell and edentulous hinge of Anodon. I 
believe this is about the oldest known Lamellibranch : occurring in considerable abundance among the Lingule 
in the slates near Tremadoc, and from being about the same size and texture may be confounded easily with 
them when crushed. 
Position and Locality—In the Lingula slates of Penmorfa, Tremadoc, N. Wales. 
Explanation of Figure —P\. 1. K. fig. 18. Natural size, two right and two left valves. 
Genus. ORTHONOTUS* (Conrad). 
Gen. Char.—Elongate, oblong, equivalve, very inequilateral ; hinge-line straight, not elevated, the margins 
erect, with an internal cartilage-plate running beneath them; ventral margin straight, or with a shallow sinus, 
from which when it exists a shallow depression extends toward the beaks; beaks moderate, near the anterior 
end, with a very deep, large, lunette beneath them, formed by the inflexion of the margins. 
I have taken the three species of Orthonota given by Hall in his Paleontology of New York as types ; 
and having on careful consideration added to them a few species of Cypricardites of Conrad and Modiolopsis of 
Hall (e.g. MW. nasuta), which are clearly congeneric, I found the group to include some of our British fossils, and 
offer the above generic character. They are distinguished from Modiolopsis proper by the deep, hollowed, 
anterior lunette, they also want the protuberant anterior adductor impression, it being inconspicuous. They 
must not be confounded with those hollow-backed shells forming the genera Grammysia (Vern.) and Sangui- 
nolites (M*Coy) in which the dorsal margins are inflected at right angles. They are, in fact, a sort of elongate 
Edmondia, differing merely in this point of habit and the existence of usually a more or less distinct sinus in 
the ventral margin and corresponding oblique hollow in the sides. 
ORTHONOTUS CYMBIFORMIS (Sow. Sp.) 
Ref. and Syn. = Cypricardia cymbaformis Sow. Sil. Syst. t. 3. f. 10 a. and t. 5. f. 6. 
Sp. Ch.—Rhomboidal, length rather more than twice the width; valves very deep, and strongly carinated 
along the slightly sigmoid, diagonal ridge, from the beak to the respiratory angle; beaks small, incurved over a 
* Written Orthonota by Conrad. 
