POLLICIPES. 57 
in Mr. Fitch’s Collection: also a single scutum sent me by Professor Steenstrup, and found 
by M. Angelin, after whose name I have called this well-marked and peculiar species. 
Scuta (fig. 7, a, 6); triangular, much elongated, considerably convex, apex extremely 
acuminated ; basal margin at nearly right angles to the straight occludent margin, but near 
to the rostral angle, it is produced in a remarkable manner into a rounded, obliquely truncated 
broad point.’ The tergo-lateral portion of the valve, formed by the upturned lines of growth, 
is not much developed: the tergo-lateral margin, as seen externally, is obscurely divided 
into two lines, of which the upper, or tergal portion, has its edge reflexed ; this same whole 
margin, however, seen internally, appears nearly straight, and this is essentially the case ; 
the projecting angle being connected with the thickening of the valve during growth. The 
exterior surface is smooth, with some faint longitudinal strize: a single ridge, or rather, 
line of flexure, runs from the apex to the baso-lateral angle. Seen internally, the upper- 
most part of the valve is found to be unusually thick and solid, with the pit for the ad- 
ductor scutorum muscle well developed, and placed rather low down. ‘The internal occlu- 
dent edge (4), marked with lines of growth, becomes close above the adductor depression 
suddenly very wide, and forms a deep furrow, which I at first thought was formed to re- 
ceive the occludent angle of the terga; but upon consideration, I feel pretty sure that this 
cannot have been the case, and I believe the furrow to be of no functional importance, but 
to result from the sharp apex of the still corrum-covered portion of the valve having been 
greatly thickened: this same upper portion has, in most specimens, in its middle, a slight 
linear furrow. On the tergal margin of the internal surface there is a small portion, marked 
with lines of growth, which is obliquely truncated, owing to the valve having become very 
thick ; and this must have overlapped the tergum. From these peculiarities in the internal 
surface of the apex of the scuta, it may be inferred, that the terga, owing to the probable 
close contact of the two valves, would present peculiarities of a corresponding nature. 
The largest British specimen is ‘8; and the Scanian specimen is ‘95 of an inch, in length. 
Terga (fig. 7, c, d); in Mr. Fitch’s collection there are, from the same formation in 
which the above scuta were found, two terga, remarkable from a very wide square-edged 
depression, running parallel to the occludent margin, which is itself rounded and pro- 
tuberant: these valves probably belonged to the P. Angelini, and anyhow may be con- 
veniently here described. Valve rhomboidal, not very flat, smooth, with a conspicuous 
ridge, wall-sided on its carinal aspect, running almost down the ‘middle of the valve from 
the apex to the basal angle, which latter is not very sharp. The upper carinal and 
occludent margins meet each other at slightly less than a right angle; occludent margin 
a little longer than the scutal margin, with its edge thickened, rounded, and protuberant 
to an unusual degree; alongside the occludent margin an unusually broad and deep, 
square-sided depression runs, equalling in width about one third of the scutal margin; a 
1 Amongst the Scanian fossils from Kopinge, there is a scutum with the whole upper part broken off, 
but which I think belonged to this species; if so, it differs from all the others in the rostral portion of the 
basal margin projecting very little. 
h 
