Dr. H. Woodivard — Cirripedes from Trimminglmm Chalk. 349 



Darwin." On examination it will be seen, however, that Darwin's 

 S. fossida is at once distinguished from these valves (which 

 I identify as near to P. striatus) by the fact that in S. fossida 

 there is a minute but well-defined longitudinal hollow groove 

 on the summit of the ridge or keel of both the scutum and 

 tergum ; the ridge on the valves in P. striatus is not grooved along 

 its summit, but is a solid well-defined ridge (as seen in Darwin's 

 figures, op. cit, tab. iv, figs. 56, c). Both scutum and tergum are 

 stout, thick valves. The general form and proportions in both 

 specimens agree best with Darwin's figures of P. striatus from the 

 Norwich Chalk. In one point these valves differ from P. striatus, 

 and that is in being less strongly ornamented by longitudinal strige; 

 but in the colour-bands and in the contour-curvature and lines of 

 growth both valves agree very well with P. striatus. They are 

 at most only a less striated variety which might be named P. pauci- 

 striatus. 



Tergum. — In the tergum (Fig. 32) there is seen a well-defined 

 raised margin along the carinal border and a broad longitudinal 

 undulation running down the valve to its baso-lateral border, which 

 is flexuous; the more or less symmetrically rhomboidal form of the 

 tergum is also modified by the strongly arcuate curvature of the 

 valve, the apex leaning towards the carinal border ; the free margin 

 of the valve is also narrower than the latero-carinal side. (In 

 S. fossida, as figured by Marsson, the crest of this valve is nearly 

 straight, and the apex inclines slightly in the opposite direction to 

 the Trimmingham fossil.) Length of tergum, 21 mm. ; extreme 

 breadth, 10 mm. ; length of base of occludent carinal border, 13 mm. ; 

 on the upper carinal border, 12 mm. The longitudinal ridge is 

 very arched, and the free border is not only narrower but more 

 steeply inclined than the occludent side; the banded ornament 

 produced by fine lines of growth is accentuated by colour-bands. 



There is a second imperfect tergum which also comes from the 

 same spot at Trimmingham, and shows rather stronger longitudinal 

 striae on the carinal side of the central ridge than the more perfect 

 valve. It is less flat than the tergum of P. Angelini, among which 

 I had in the first instance placed it, and it may possibly belong to 

 P. striatus. 



Scutum (Fig. 31). — Rather thick, subtriangular, tumid, and curved, 

 apex acute, basal margin straight, 10 mm. broad, forming a right 

 angle with the lateral margin which is 9 mm. long ; tergal m argin 

 also 9 mm. long, both margins rather concave ; a strongly marked 

 rounded ridge separates the valve longitudinally from the apex to 

 the latero-basal angle into two unequal parts, while a second less 

 prominent line 5 mm. apart divides the occludent side of the scutum 

 into two equal parts, the inner half being marked by seven longi- 

 tudinal lines, the outer half having only horizontal lines of growth ; 

 the lateral side is also marked by a series of less prominent 

 longitudinal lines. All these longitudinal strife describe a strong 

 curve, the convexity being towards the occludent margin. Colour- 

 bands mark both the scutum and tergum, running parallel to the 



