44 FOSSIL CIRRIPEDIA. 



The valves all have their surfaces plainly ribbed longitudinally ; the ribs are narrow, 

 and as they cross each zone of periodical growth they are tuberculated. 



Carina (fig. 1 0, h, c) ; narrow, tapering, little bowed inwards ; tectum in a transverse line, 

 steeply arched, not carinatcd ; basal margin bluntly pointed ; in very young specimens, 

 however, it is evident from the lines of growth, that the basal margin must have been 

 rounded; the parietes are inflected, and rather narrow, being barely half the width of 

 half the tectum; they are plainly marked by parallel lines of growth ; internally the valve 

 is rather deeply concave ; no part of the apex projected freely. 



Scufa (fig. 1 0, e) ; umbo of growth on the occludent margin, at about one third of the 

 entire length of the valve from the apex ; somewhat convex ; four-sided, the margins 

 consisting of the lateral, which is considerably longer than the other sides ; the basal 

 which forms nearly a right angle with the lower half of the occludent margin ; and 

 of an upper and lower occludent margin, meeting each other at about an angle of 135° : 

 the margin which I have here called the upper occludent, homologically corresponds with 

 the tergal margin of the other cretaceous species, and with the upper, nearly straight, 

 portion of the occludent margin in the tertiary S. magnum and the recent B. vidgare, — 

 a fact which has been mentioned under the head of Scalpellurn. The edge of the upper 

 occludent margin forms a strongly prominent ridge, with its apex forming a slight pro- 

 jection ; a second less prominent ridge runs from the umbo to the baso-lateral angle, and a 

 third faint ridge runs from the umbo to a point in the basal margin, nearer to the rostral 

 than to the baso-lateral angle. Internally there is a rather deep hollow for the adductor 

 muscle ; along the under surface of the upper occludent margin there is a slightly 

 prominent ridge, bordered by two slight depressions. 



Terffa (fig. 10, a); flat, elongated diamond-shape; close and parallel to the occludent 

 margin there is a narrow, very prominent ridge or plait, the end of which forms a slight 

 projection; a straight ridge runs from the apex to the sharp basal angle; the scutal and 

 lower carinal margins are of equal length, and longer than the occludent and upper carinal 

 margins, which latter are equal, and meet at an angle very slightly less than a rectangle. 

 On the under surface there is a slight depression and ridge, close and parallel to the 

 occludent margin. I have no doubt that the ridge along the upper occludent margin of 

 the scuta, and that on the occludent margin of the terga, together with their projecting 

 points, are related to each other, owing to the close contact of these valves.^ 



' 14. SCALPELLUM SEMIPOECATUM. Tab. I, fig. 6. 



S. carind ignotii : scuti cos f is duobus ah umhone ad angulvm hasi-Jateralem et ad marc/inis basalts 

 medium decurrentibus : sujoerjicie infer hanc costam et maryinem ocdudentem lineis tenuibus, lonyitudinalibiis, 

 elevatis instructd. 



Carina unknown : scutum, M'ith two ridges running from the umbo to the baso-lateral angle, and to 



