T. II. Withers — The Cirripede Brachylepas cretacea. 325 



just below the pit for the adductor muscle, and meets the ridge formed by the 

 inner occludent margin just above the pit, thus forming an obtusely angular 

 depression (marked by lines of growth) for the reception of the tergo-lateral 

 angle of the tergum. External surface marked by somewhat irregular, feeble 

 transverse ridges, which appear to become more regular and prominent in the 

 larger valves. 



Tergum (Fig. 5) sub-rhomboidal, divided into almost equal portions by 

 a prominent ridge curving from the apex to the basal angle, formed by the valve 

 being sharply bent along this line ; apex pointed and curved towards the scuta ; 

 lower part of valve narrow and pointed ; upper carinal margin generally 

 considerably convex, and usually shorter than the lower carinal margin ; 

 occludent margin shorter than the scutal margin. A portion of the valve along 

 the occludent margin is rounded and protuberant, and is bounded by a depression 

 running from the apex to the scutal margin at a point about one-fourth the 

 distance from the occludent margin, to which extent the valve was overlapped 

 by the scuta ; a further indistinct fold or ridge runs from the apex to about the 

 middle of the scutal margin. Valve externally marked with transverse ridges 

 like the scutum, forming an acute angle on the central ridge. Inner surface of 

 upper carinal margin thickened to a very small extent and marked by lines 

 of growth. 



Upper latus (Fig. 4) a very acute-angled isosceles triangle. External surface 

 almost smooth, and marked with irregular, indistinct, transverse ridges or 

 periodic lines of growth, more strongly marked on the lateral margins. The 

 lines of growth are continued on the inner surface, where they are very 

 obliquely upturned, and meet on a raised, sharp-edged, median ridge, which 

 extends to the. apex. The portion marked with lines of growth indicates the 

 extent to which the valve overlapped the scuta and terga, the raised ridge 

 falling in between ; and the small triangular smooth portion near the base 

 indicates the extent to which the valve was covered by the corium or membrane 

 lining the inside of the valves. 



Valves of the Lower Whorls. — Although the specimen of Brachylepas Naissanti, 

 figured by Dr. H. Woodward as B. cretacea (Geol. Mag., 1901, PI. VIII, 

 Fig. 4fl), shows at the base of the eapitulum from three to four whorls of 

 imbricating valves in position, little knowledge can be gained of their inner 

 structure. The specimen shows admirably the external arrangement of these 

 valves, as well as their variation in shape and size, and enables one to gain some 

 idea as to the number of valves constituting the several whorls. On the more 

 complete side of the specimen figured there are fifty-four valves preserved, and 

 if we reckon the same number for the other side the total would be 108. 

 In all probability the number was greater, since some of the valves near the 

 carina have a median notch in their basal margin, presumably for the external 

 fixation of another valve. 



From the specimens from Liineburg we learn that the lower whorls of 

 imbricating valves were probably four in number, with a few additional valves 

 below the upper latera. The valves decrease in size outwardly, their bases 

 stand almost on the same plane, and the median ridge of the outer valve closely 

 corresponds to that of the valve immediately in front of it. When the valves 

 were in position their external walls must have inclined at a greater angle than 

 the walls of the carina and rostrum. All the valves have a strong median ridge 

 with laterally divaricating growth-bands, which give to the lateral borders 

 a serrated appearance, a feature strongly marked in certain valves. The median 

 ridge sometimes stands out at the apex as a short spine. 



Leaving out of consideration the additional valves below the upper latera, the 

 innermost whorl is composed of valves that have a median semicircular notch 

 in their basal margin (Figs. 7-9) ; some of these valves (Figs. 8, 9) have their 

 inner surface thickened to form a sharp median ridge extending from the apex 

 generally to about two-thirds the length of the valve, at which point a further 

 ridge extends to each basi-lateral angle ; others have their inner surface almost 

 flat (Fig. 7). Surrounding this is a whorl of valves possessing an inwardly 

 projecting angular ledge (Fig. 10), which is fixed into the median notch of the 



