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, b) ; 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 striae : 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 ((5), 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 corium-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. 



Tertja (fig. 1 , 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. Anr/elini, 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 



