POLLICIPES. 61 



11. POLLICIPES GLABER. Tab. Ill, fig. 10. 



PoLLiciPES GLABER. Roemer. Norddeutsch. Kreidegebirg. Tab. xvi, f5g. 11. 

 XiPHiDiUM MAXIMUM. J. Sowerbij. Dixon's Geology of Suffolk, Tab. xxviii, figs. 6—8. 



P. scutis subtemiibus, latiusculis, adformam trianguli aquianguli accedeniibus ; margine 

 hasali non prorsus redo; tergo-laterall segmento e zonis incrementi reflexis formato, 

 ubi latissimo, reliqiia valva dlmidbrm aquante : margine tergali apicis intm sulcato. 

 Carince margine hasali obtuse acuminato. Lateribus superioribus triangulis, tertiam partem 

 longitudiiiis tergorum cBquantibus. Lateribus dtiticis inferioribus singulis costd prope termi- 

 num margin is basal is decurrente. 



valve sloping from it,) runs from the apex to the sharp basal angle : this ridge is very slightly curved in 

 two directions, like the letter S, it runs at about one third of the entire width of the valve from the 

 carinal margin. 



Carina (fig. 9, e,f) strong and solid, with lines of growth conspicuous on its surface ; very slightly arched 

 inwards ; triangular, moderately tapering ; transversely moderately convex, very plainly carinated, with a 

 slightly projecting rib ; on each side, at a little distance from the lateral edges, there is a distinct and linear 

 furrow, and these edges themselves are, partly in consequence, rounded and slightly protuberant : basal 

 margin square, and not at all protuberant. Internally, the upper part, for about one third of the total length 

 of the valve, must have projected freely, and has been filled up solid with a trace (/) of a central crest : 

 the internal lateral edges are slightly scalloped out along the whole length of the valve. 



Rostrum (fig. g, k, i) ; broad, triangular : apex curled inwards to a most remarkable extent, so as even to 

 point a little downwards ; basal margin just perceptibly protuberant, with a square projection formed by the 

 end of a wall-sided, broad, flat-topped ridge, running down from the apex ; Phillippi, however, states, that 

 the form of the basal margin varies. Internally, a full upper half of the valve projected freely ; the internal 

 upper surface is smooth and concave, with just a trace of a fine central crest : the inwardly curled apex 

 converts the upper part into a hood : the central basal projection is channelled, the channel running a little 

 way up the valve, and being gradually lost : this channel, no doubt, allowed a filament of the corium to pass 

 to the sub-rostrum. 



Peduncle. Dr. Phillippi has sent for my inspection, a rare and interesting specimen of a peduncle, 

 with the scales preserved, no doubt, belonging to this species. The scales, as usual, decrease downwards in 

 size ; they are rather broad ; each has its upper end rounded ; is marked transversely by lines of growth, 

 and has a slight external, central, longitudinal crest : this crest is wedge-formed, being widest at the 

 apex. I have not seen this latter character in the peduncular scales of any other PoUicipes ; there are, how- 

 ever, traces of it in the small lower Latera in P. mitella; it is apparently caused by the lateral overlapping 

 of the closely-packed scales, and chiefly when the specimen was young. 



Affinities. The general form of the carina, with its lateral furrows and rounded protuberant margins, — its 

 carinated central line ; — the shortness, and great inward curvature of the rostrum, with its strong, central 

 ridge, terminating in a channelled projection on its basal margin — show a clear affinity between this species 

 and the recent P. mitella of the Eastern tropical seas. There are some points of resemblance in the scuta and 

 terga to the same recent species ; but in the scuta a closer affinity is shown to P. dorsatus ; and in the terga 

 to those described under P. elongatus : in the manner, moreover, in which the upper part of the carina is 

 filled up and furnished with a central crest, there is a relationship to P. validus. The affinity of P. carinatus 

 to P. mitella is interesting ; because we may with some confidence infer from the relationship between 

 P. carinatus, dorsatus, validus, and rigidus, that, in these several species, the valves, which hitherto have 

 been found only separated, were united together to form the capitulum in a somewhat similar manner as in 

 the well-known recent P. mitella. 



