FOSSIL CIRRIPEDES. 939 



a.bove the umbo extending almost parallel to the upper occludent 

 margin ; apical portion usually constricted and acute ; basilateral 

 a.ngle shortly and obliquely truncated. Tergum subrhomboidal, 

 with its upper half curved towards the scuta ; basal angle 

 sometimes acute, but more often shortly and obliquely truncated. 



MMerial. — Two almost complete capitula and nine portions of 

 others. All of these appear to be immature, and there is also a 

 large series of isolated valves. 



Holotype. — The nearly complete capitulum, I, 15830 (PI. XOIV. 



Distribution. — Cambridge Greensand : Cambridge; Cenomanian, 

 Chalk Marl : near Cambridge, and Burham, Kent ; Cenomanian, 

 A. 7)/e?^a-marls : Oxted, Surre}^, and Wantage, Berkshire; [? Ceno- 

 manian], Chalk detritus : Charing, Kent. 



Measurements. — The two nearly complete capitula (PI. XCIV. 

 fiijs. 11, 13) each measure 4 mm. from the apex of the scutum to 

 the base of the lowest whorl of latera, and the uncrushed 

 capitulum (PL XCIV. fig. 11) measures 4-2 mm. in breadth. 

 Bjth are immature examples. Among the detached valves the 

 largest examples of the upper series measure respectively : — 



Carina, I. 15820. Length (valve slightly broken at apex) 

 5 '9 mm. ; breadth 1*7 mm. 



Scutum, I. 15822. Length (from apex to lowest point of basal 

 margin) 6*4 mm. : breadth 4'5 mm. 



Tergum, I. 15833. Length 7Q mm.; breadth 3*4 mm. 



Upper latus, I. 15834. Length 4*5 mm. ; breadth 3"2 mm. 



There are, however, several fragments which show that these 

 valves attained somewhat larger dimensions. A comparison of 

 these with the proportions of the valves, as shown in the nearly 

 complete capitulum, seems to show that the ca,pitulum of the 

 species reached a length of at least 15 mm. 



Description of valves. — Valves thin, smooth, or ornamented 

 with excessively fine ridges radiating from their umbones. 



Carina (PI. XCIV. figs. 1, 2) narrow, widening gradually 

 downwards from the apex to the basal margin, either slightly 

 bowed inwards, straight, or bowed outwards, not divided off into 

 parietes and intraparietes ; basal margin acutely angular; tectum 

 slightly to moderately convex transversely ; in some carinas there 

 is a strong, rounded, median, longitudinal keel, nearly as wide as 

 the portion of the valve on either side, but in some specimens 

 it is less strongly marked and in others barely perceptible. Inner 

 surface somewhat thickened near the apex and marked with 

 obliqvie growth-lines ; the extent of the surface thus thickened 

 varies, and at the most is one-third of the length of the valve; 

 the valve therefore projected freely to a variable extent. 



Scutum (PI. XCIV. figs. 3-6) varying in shape from sub- 

 triangular to trapezoidal, moderately convex transversely, the 

 surface of the valve sloping more steeply from the umbo to the 

 lateral margin ; umbo situated just below the apex in young 

 specimens, and in mature examples usually occupying a position 



