CYPROSINA. 53 



mark. The somewhat similar furrow in the Entomididae is dorsal. The form 

 described below is, I believe, the only species of this group which is at present 

 known. 



1. Qenus — Cypeosina, Jones, 1881. 



1. Cypeosina "Whidboenei, Jones. PL IV, figs. 1 a — c, 2 a — c, 3, 4. 



1881. Cypeosina Whidboenei, Jones. Geo!. Mag., dec. ii, vol. viii, p. 338, pi. ix, 



figs. 1—3, 5. 

 1888. — — Etheridge. Foss. Brit., vol. i, Pal., pt. 1, p. 430. 



Description} — Carapace bivalved, large, ovoid, slightly narrower at the 

 anterior end. Test thick. Surface smooth, furrowed by a short transverse sulcus 

 slightly behind the centre of each valve, indenting the ventral margin, and 

 extending half way upwards across the long diameter. Margin of valve steep, 

 incurved. Dorsal edge evenly convex ; posterior edge slightly tapering ; ventral 

 edge nearly straight ; anterior margin bearing a beak which is rounded above and 

 indented below, distinct though not large, varying in its prominence according to 

 the contour of the front margin (figs. 1 a and 2 a), and formed, as it were, 

 by a slight but definite lateral pinching in of the middle of the front extremity of 

 the two valves, rather than by a notch cut out of their curved and projecting end. 

 Dorsal edge of the left valve overlapping that of the right, with a small groove 

 and very fine hem at the posterior edge ; dorsal margin of the right valve 

 having a linear groove along its whole length, where the overlapping valve meets 

 it. The antero-ventral margin of each valve turning sharply inwards and 

 upwards to a slight extent, and having a feeble marginal hem, an antero-ventral 

 longitudinal furrow being thus caused in the closed carapace continuous with the 

 antennal notch. Ventral margins meeting apparently without overlap. 



Muscle-spot irregularly circular, consisting of a more or less distinctly 

 reticulated centre with numerous (more than twenty) alternately opaque and sub- 

 translucent radiating plumose lines (the former having sometimes the appearance 

 of low ridges), longer on the upper side, shorter below, obsolete posteriorly, and 

 passing into a local reticulation in front (figs. 3 and 4). 



Size. — The larger figured specimen (fig, 2) measures 19 mm. long. Another 

 specimen (fig. 1) measures 17 '5 mm. long. 



Localities. — Lummaton, where it is common. A single specimen from Wol- 

 borough is in Mr. Vicary's Collection. 



' This description is partly taken from the notes published by Prof. Eupert Jones in the ' Geol. 

 Mag.,' loc. cit. 



