POLLICIPES, 55 
pression for the adductor scutorum does not appear to have been deep: the concavity of 
the valve extended to the apex, with the upper part not filled up solid; a considerable 
portion of the upper tergal margin is marked by lines of growth, and must have over- 
lapped the tergum, but there is no trace in it of a recipient furrow. 
Affinities. This species seems quite distinct from all others; and I can hardly say to 
which species it is most related; in some few respects it comes nearest to P. acuminatus.' 
16. Potticipes ELoNGatTus. Tab. ITI, fig. 5. 
PoLLICIPES ELONGATUS. Steenstrup. Kroyer’s Tidsskrift, b. i, p. 361. 
_ Lz&vIs (Sowerby). Ib. Ib. b. ii, p. 409, pl. 5, figs. 9, 10. 
P. scutis pene quadratis ; margine occludente et parte inferiort marginis tergo-lateralis rectangulé ad 
marginem basalem positis ; apice obtuso. 
Scuta almost square; occludent margin and the lower part of the tergo-lateral margin at right angles 
to the basal margin ; apex blunt. 
White Chalk, Denmark. Mus. Univers. Copenhagen. 
General Remarks. Professor Steenstrup at first described this species as distinct, but subsequently con- 
sidered it the same with P. /evis of Sowerby; this is not the case, and therefore I have retained the name 
first given, though very inappropriate to the more important valve. According to the practice here followed, 
the species is founded on the scutum, of which a mere fragment and impression exists, but it is sufficient 
to show that it is distinct. In the same chalk with this scutum, there are two terga which are different 
from any other seen by me, and which Professor Steenstrup has described as belonging to this species, a 
view which I have followed with some hesitation. 
Scutum (fig. 5, c, 6), nearly smooth, but with the growth-lines plain ; thin, very slightly convex ; oblong, 
almost rectangular, but with the upper lateral corner rounded off. Occludent and lower part of tergo-lateral 
margin both straight, and at right angles to the straight basal margin: upper part of tergo-lateral margin 
much arched and protuberant, which, together with the blunt apex given to the valve, itis almost rectangular, 
oblong outline. A trace of a ridge runs from the baso-lateral angle to the blunt apex. The figure 
given is a restoration ; being guided by the outline impressed on the chalk, and the lines of growth as seen 
on the small baso-lateral preserved portion. 
Tergum (fig. 5, a), convex, thick, elongated, sub-rhomboidal, or rather triangular, for the upper and lower 
carinal margins blend into each other with quite a uniform and gentle sweep: upper part of the carinal and 
occludent margins meet at an angle of about 45°; from the apex to the sharp basal angle, an angular, very 
slightly curved, conspicuous ridge runs at about one third of the entire width of valve from the carinal 
margin: the surface of the valve slopes rather steeply away on both sides from this ridge. Occludent and 
scutal margins about equal in length; parallel to the former, a rather wide space of the valve is slightly 
depressed, with a corresponding portion of the scutal margin slightly indented; the occludent margin 
itself is not rounded and protuberant, as if it had been received in a furrow in the scuta. A considerable 
portion of the upper part of the valve projected freely. This valve more resembles the homologous one in 
the Italian tertiary, P. carinatus, than that of any other species: as before stated, I assign it to this species 
on the excellent authority of Professor Steenstrup; I may, however, remark, that it appears much thicker 
and stronger than the scutum. The figure of the tergum (a) is not very good, and has been drawn on too 
small a scale. 
