FOSSIL CIRRIPEDES. 535 



intraparietes bent inwards and meeting for about one-fourth the 

 length of the valve from the apex, upper part of valve solid and 

 freely projecting. Scutum with tergo-lateral angle almost in line 

 with the middle of the valve. Tergum subrhomboidal, a delicate 

 furrow extending from the apex to the basal angle. Upper latus 

 subtriangular, apex acutely angular, slightly bowed towards scuta, 

 basal margin i-ounded. Rostral latus acutely angular transversely, 

 about 2-7 times as long as wide. Rostrum subtriangular, with a 

 strong median keel extending from the apex, widening towards 

 the convex basal margin. 



Description of valves. — Carina narrow, widening gradually from 

 the apex, considerably bowed inwards, basal margin obtusely 

 V-shaped. Tectum flatly-arched tiunsversely, obscurely carinate, 

 and ornamented with numerous fine longitudinal ridges. Parietes 

 ntirrow, less than half the width of tectum, not longitudinally 

 ridged, bent almost at right angles to the tectum, slightly concave. 

 Intraparietes very narrow, bent inwards almost at right angles, 

 the inner niargins meeting about one-fourth the length of the 

 valve from the apex, above which the valve is solid and must 

 have projected freely. 



Scutum moderately convex, divided unequally by a prominent 

 ridge running from the apex to the basi-lateral angle, the basi- 

 lateral angle being slightly produced. AjDex acuminate. Basal 

 margin sinuous, about two-thirds the length of the valve ; 

 occludent margin slightly convex and nearly parallel to the lateral 

 margin ; tergal and lateral margins of almost equal length and 

 forming an angle of about 145°, either margin being about half 

 the length of the valve. Surface of valve ornamented with fine, 

 closely-set, longitudinal ridges ; a narrow slip along the tergal 

 margin is somewhat bent downwards and is devoid of i-idges, 



Tergum sub-rhomboidal in general outline, slightly convex, 

 with a delicate furrow extending from the apex to the basal 

 angle. Apex and basal angle acuminate, more so than is indicated 

 in Darwin's original figure ; scutal angle somewhat pi'otuberant, 

 Carinal margin convex ; scutal margin sinuous, longer than the 

 occludent margin, which is neai'ly straight. Surface of valve 

 ornamented with numerous fine longitudinal ridges. Inner 

 surface, in the region of the apex, is marked on its edges with 

 oblique lines of growth, these indicating the extent to which the 

 valve projected freely. A little below the apex, nearer to the 

 occludent margin, are three or four small ridges ending abruptly 

 about one-fourth the length of the valve from the apex. These 

 ridges were evidently connected with the firm attachment of the 

 corium, or membrane which lined the inner surfaces of the valves, 

 and are homologous with the series of tubercles on the inner 

 surfaces of the terga of S. darwiniammi Bosquet. 



Upper latus subtriangular, slightly curved towards the scuta, 

 almost flat transversely, convex longitudinally ; umbo slightly 

 projecting, with a thick ledge formed beneath it, which thins out 

 towards the lateral angles ; tergal margin slightly convex ; scutal 



