30 FOSSIL CIRRIPEDIA. 



covered by a lateral projection of the central portion : a tolerably distinct ridge runs from 

 the apex to the baso-lateral angle. Amongst the several specimens from Hanover sent me 

 by Drs. Dunker and Roemer, the scuta all belong to the First variety. 



I believe all these differences in the scuta of the three varieties ensue partly from the 

 varying acumiuation of the upper part, and consequently of the extent to which the apex 

 projected freely, but chiefly from the degree to which the upper part of the valve above 

 the adductor muscle has been internally thickened. In the first variety the upper part is 

 simply concave, and the pit for the adductor very shallow ; in the third variety, the same 

 upper part is highly prominent, and apparently as a consequence the internal occludent 

 edge is deeply furrowed ; the pit for the adductor muscle is deepest in the second variety. 



The above differences would perhaps affect the outline of the terga, but I am not able to 

 follow the precise manner ; nor should I have thought them sufficient to have produced the 

 amount of variation presently to be described in the terga ; but possibly other scuta may vary 

 still more. At first I concluded that the upper part of the inner occludent edge, which in 

 Var. Ill is deeply furrowed, received in it the occludent edge of the tergum (as the furrow 

 on the tergal side of the apex of the scutum receives the edge of the tergum in the recent 

 FoUicqjes mitella), but this on consideration I do not think can possibly be the case, 

 although it would amply account for the variation in the terga. 



Terga. I have seen great numbers of these valves ; eight specimens are in Mr. Fitch's 

 collection from Norwich ; one is figured by Mr. J. Sowerby in the ' Min. Conch.,' (PI. 606, 

 fig. 6,) and they are numerous in the collection from Scania and Hanover, These valves, 

 which, as stated in the preliminary remarks, present a most remarkable amount of variation, 

 will be best described under three distinct heads. 



Variety I. Tab. II, fig. 5. This valve, from its greater width and smoothness, 

 compared with the other varieties, perhaps belongs to the typical S. maximum. Surface 

 smooth, with a mere trace of some longitudinal striae, sub-rhomboidal, elongated, with the 

 apex much produced and curled towards the carina ; nearly flat ; the occludent margin 

 arched, nearly equal in length to the scutal margin ; upper carinal margin hollowed out, 

 about half the length of the lower carinal margin ; the occludent and upper carinal margins 

 meet each other at a very small angle, making the apex almost horn-like ; from it to the 

 bluntly pointed basal angle, a slight rounded ridge, and on the carinal side of it a slight 

 furrow, (both becoming less plain towards the lower part of the valve,) extends. As seen 

 internally, the thickness of the valve, in its upper part, varies ; a rather large upper part 

 projects freely. A rim along the occludent margin is rounded and slightly protuberant, 

 with a slight depression in the valve parallel to it. Length of the largest specimen I "2 of 

 an inch. 



This variety is found commonly near Norwich, in Scania, and Hanover. 



Tergum. Variety 11. Tab. II, fig. 0. The valve in this variety (from near 

 Norwich) is much elongated, sub-triangular, approaching to crescent-shaped; lines of 

 growth conspicuous, with a few very faint longitudinal striae. Carinal margin not (or 



