POLLICIPES. 53 



lower carinal margins compared with the upper carinal and occludent margins of the 

 terga, and lastly in the basal margin of the carina being truncated; it differs from P.planu- 

 latiis of the Oxford Clay, and therefore its other nearest relative in age, by the basal angle 

 of the terga being rounded, instead of square as in that species. 



the two broad arched roof-sides ; and in these slips the lines of growth run almost parallel to the inner 

 margin of the valve : ia this respect the valve approaches in character to that of Scalpellum. The heels or 

 baso-lateral angles apparently projected slightly, as I infer from a slight downward curvature in the lines 

 of growth, along a line corresponding with the heel, and separating the roof-part from the inflected walls 

 of the carina. 



Sub-carina (fig. 11, </) : in Professor Steenstrup's collection there are several worn valves which appear 

 to have been sub-carinfe ; in shape approximately semi^conical ; the basal margin being almost semi-oval> 

 with the two corners a little inflected ; hence the valve is deeply concave to an unprecedented degree, and 

 this is quite conformable with the singular sectional outline of the carina (c). About one fourth part of the 

 length of the valve must have projected freely ; the outer surface is longitudinally ribbed, and the lines of 

 growth remarkably undulatory. 



Rostrum (fig. 11, e) : this valve which I believe to be the rostrum resembles the sub-carina, but is more 

 open, less high, and with a larger proportion, namely half, of its entire height freely projecting ; the semi-oval 

 basal margin is slightly sinuous, the projecting points corresponding with the external longitudinal ribs. 



Length of carina, 1'5; of the largest of the sub-carinse, '6 ; of the largest rostrum, "45 of an inch. 



4. PoLLiciPES Hausmanni. Tab. Ill, fig. 3. 



PoLnciPES Hausmanni. C. L. Koch and Bunker. Norddeutsch. Oolithgebilder, p. 52, Tab. vi, fig. 6. 



— — F. A. Roemer. Versteinerung. Norddeutsch. Oolithengebirges, p. 211, Tab. iv, fig. 2. 



P. scutis subtriangulis, angulo baso-laterali valde rotundato ; apice producto ; margine basali cum 

 margine occludente angulum pcene rectum formante ; internd apicis superjicie prominente, margineque 

 tergali sulcata. 



Scuta, subtriangular, with the baso-lateral corner much rounded, and with the apex produced ; basal 

 margin forming nearly a right angle with the occludent margin ; apex with its internal surface prominent, 

 and with the tergal edge furrowed. 



Hilsthon, des Elligser Brinkes. (Lower Greensand, Germany.) 



Messrs. Koch and Dunker have given a full and detailed account of this species, together with truly 

 excellent figures, and I have nothing to add to their remarks, but will re-describe, for the sake of uniformity, 

 the valves of this species, which, through the kindness of Professor Steenstrup and Pi-ofessor Dunker, 

 I have examined. The valves are slightly worn. The figures given in tab. Ill are not, I think, so good as 

 most of the others. 



Scuta (Tab. Ill, fig. 3, h, c) moderately convex, sub-triangular ; apex much acuminated, slightly 

 curved towards the terga ; surface smooth, faintly marked with zones of growth, and, especially near the 

 apex, with faint lines and furrows radiating from it. There is no distinct ridge proceeding from the 

 apex to the baso-lateral angle, which is so much rounded that the basal margin blends into the tergo- 

 lateral ; it must, however, be remarked, that the specimens are worn. The occludent margin stands at 

 right angles to the basal ; and the lower part of the tergo-lateral margin forms rather above a right angle 

 with it. Internally (c), there is a deep pit for the adductor scutorum, and in the upper part, close to the tergal 

 margin, a deep furrow ; the central portion is prominent ; the occludent margin keeps nearly of the same 

 thickness up to the apex of the valve. 



Terga (Tab. Ill, fig. 3, d), nearly flat, sub-rhomboidal, or rather pointed oval, with the scutal half 



