Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/247

Rh J. S. GARDXER OX BRITISH CRETACEOUS PATELLID^ ETC. 199

Emarginttla axcistra, sp, nov. Upper Greensand. PI. VIII. figs. 23, 24.

Very elevated, Phrygian-cap-shaped, compressed laterally, hol- lowed out under the beak in form of a semicircle ; apex much re- curved, pointing downward and projecting considerably beyond the posterior margin ; sculpture, 8 principal and about 14 subordinate ribs, reticulated by fine transverse lines of growth, the sculpture being most distinct anteriorly, whilst the posterior region is nearly smooth. The fissure is long and narrow ; the fissural region nearly flat, slightly depressed, smooth, and bordered by two raised ribs.

This well-marked form is quite distinct from all others of our Cretaceous rocks. E. dubisiensis, P. & C, resembles it slightly, but has a more inrolled apex, and differs in its ornamentation.

The species is described from a unique fossil from Round way, near Devizes, in the Bowerbank collection at the British Museum. E. capidiformis, now living in the Mediterranean, is of smaller size, but identical in form with this species.

Emargixula Meteri, sp. nov. Chloritic Marl. PI. VIII. figs. 14, 15.

Shell cap-shaped, very elevated, laterally compressed, the sides being almost flat, convex anteriorly, much hollowed out posteriorly ; apex sharp, beak-like, recurved, overhanging posterior margin. Fissure short ; the fissural scar is broad and depressed, but with a very slight median elevation or ridge. The cast has traces of rather coarse ribs reticulated with transverse lines, which are closer together than the ribs.

In general form this shell rather resembles E. stenosoma^ De Ryckholt, but is more concave in front and rather longer in propor- tion to its elevation; E. stenosoma has 36 ribs and 16 transverse lines, which produce a vertically elongated cancellation, with nodes at the intersections.

AVe are indebted to Mr. Meyer for the discovery of this and many other interesting forms. It is from near Lyme Regis.

Emargixula txicostata, Seeley, MS. Upper Chalk. PI. VIII. figs. 25, 26.

Thin, ovate, Phrygian-cap-shaped, compressed laterally, hollowed out posteriorly ; apex acute, recurved, overhanging posterior margin ; sculpture reticulated, consisting of ribs and lines of growth, the ribs being most strongly marked on the anterior region, whilst under the apex they are hardly visible. The fissure is very short ; the fissural scar is in the form of a ridge, between two narrow depres- sions.

This species very strongly resembles E. sanctce-catharincB, but is more depressed and more finely ornamented, and the ribs are about twice as numerous. They both have affinities with E. locidata, De Ryckh., which, however, has fewer and less regular ribs, and with E. Desori, P. & C.