Kirkbya annectens, Jones & Kirkby.

4. Kirkbya annectens, Jones & Kirkby.

(Pl. III. figs. 7, a—d; and var. bipartita, figs. 8, a, b.)

Kirkbya annectens, J. & K ., 1866, Ann. & Mag. Nat. Hist. ser. 3, vol. xviii. p. 42.

Kirkbya annectens, J. & K ., 1867, Trans. Geol. Soc. Glasgow, vol. ii. p. 220; and bipartita , 1871, vol. iii. Suppl. p, 28.

Kirkbya annectens and K. bipartita, Armstrong and others, 1876, Catal. W.-Scot. Foss. p. 44.

Valves suboblong in outline, rather convex and lobed, height half the length or more. Dorsal border straight or slightly incurved, and about two thirds of the maximum length; ventral border either straight or slightly incurved, or as slightly convex; extremities rounded and in some speci ­ mens nearly alike, in others the anterior is the more acute.

The medio-dorsal portion of the valve is depressed, and in front is a rounded boss-like lobe, and behind is another lobe or tubercle, usually smaller than that in front; the ventral portion of the valve is swollen, and traversed longitudinally by a curved ridge or rib. Lateral contour subcuneiform. Shell rather- thin. Surface smooth so far as known. Length 1/30 inch. Edge view (figs. 7 b, c, and 8 b, lateral contours) compressed, ovate.

The above description applies more correctly to the Irish members of this species. Scotch examples show some differ ­ ences; instead of two lobes or tubercles they sometimes have three, cither all on the dorsal region of the valve or with the middle one rather lower down than those at the ends, ami two (or at times three) strong ridges sweep across the valve concentrically with the extreme and ventral borders; the uppermost of these is occasionally fully above the median line of the valve, and the lowermost often takes the form of a marginal rim. The surface also, in some examples at least, is reticulated. It may be that these specimens represent a Scotch form specifically distinct from the others. This is a point for further investigation. For the present we designate it K. annectensy var. bipartita.

The Irish specimens we have seen were collected and submitted to our inspection by the late Sir Richard Griffiths. They are very uniform m character, all of them having the two bosses or tubercles, one towards each extremity of the valve, and but a single ventral rib. They have rather a Beyrichian look, and undoubtedly come nearer that genus than other members of the group under description.

Localities.—Ireland. In Lower-Limestone Shales, Drumard, Londonderry; Cultra, Down; Larganmore, Mayo.

Scotland. Carboniferous Limestone (Lower): Brockley, Lanarkshire; Orchard, Gare, in Lanarkshire; River Avon below Kinneil Mill, Linlithgowshire.

England. Hurst, near Richmond (bipartita) Yorkshire, on the authority of Mr. G. R. Vine (Proc. Yorksh. Geol. Polyt. Soc. 1883, p. 237).

Dr. C. W. Gumbel’s Kirkbya alpina , figured in his ' Kurze Anleitung zu geol. Beobacht. in den Alpcn,’ 1878, p. 83, fig. 28, has a distant resemblance to K. annectens , but is much more like Beyrichia arcuata (Bean) , as far as the little woodcut shows. It is from the Bellerophon-Iimcstone, a passage-bed from the Palaeozoic to the Mesozoic (between the Permian and the Trias).