260 Mr. T. H. Withers on 
would convey a very inadequate idea as to their size; probable 
measurements are therefore given :— 
Actual, Probable, 
in mm. in mm. 
Carina (In. 18980).... Length 12:4 13:0 
Breadth A'l(atabout4 5:0 
mm.from 
base). 
Carina (In. 18981).... Length 12:3 14:2 (as shown 
by impres- 
Breadth 5:2 .. sion). 
Subearina (In. 18983). Length 3°38 a; 
Breadth 2:0 ae 
Tergum (In, 18984) .. Length 144 170 
Breadth (cirea) 6°0 6:0 
Description.— Carina semicylindrical, moderately bowed 
inwards, strongly convex transversely, imperceptibly keeled 
in its upper half, the valve tapering rapidly towards the apex, 
which is sharply pointed; basal margin moderately convex. 
Outer surface marked with regular, widely-spaced, prominent, 
raised ridges or zones of growth, which show, especially in 
one valve (In. 18981), a tendency to become broken up into 
bead-like prominences. Fine transverse and longitudinal 
lines are to be seen between the main ridges, but the longi- 
tudinal lines are not so well marked as in the terga. The 
valve is marked, especially in its lower part, with irregular, 
closely set, fine puncte. 
Scutum.—On the specimen In. 18986, lying near a right 
tergum, was a badly crushed and shapeless valve, evidently 
showing its inner surface. At its base could be discerned 
one or two rather long and straight furrows, and these 
suggested to me that the fossil represented another kind of 
valve. It was possible to clear away most of the minute 
fractured particles of shell, and there was then exposed some 
eight or nine prominent, straight, equidistant furrows. A 
plaster-cast taken from this impression shows that the furrows 
represent the widely-spaced ridges or zones of growth such as 
are seen on the carina and tergum above, except that they are 
straighter and longer, and there is no doubt that we have 
here an impression of the outer surface of a scutum of the 
type seen in the species known as Pollicipes aalensts, Polli- 
ctpes ooliticus, and Archeolepas quenstedti. 
Tergum subtriangular, slightly convex transversely, com- 
paratively long and narrow, with prominent, widely-spaced, 
transverse ridges, which form an acute angle of which the 
apex is situated about one-third the distance from the carinal 
margin ; there 1s no definite apico-basal ridge or fold. Carinal 
ie 
