40 FOSSIL CIRRIPEDIA. 



what appeared to be upper latera, but as I could not remove them so as to examine their 

 under sides, I am far from sure that they were not broken, angular portions of scuta. If 

 we look to the character of the separate valves, there is a striking and important resem- 

 blance between the scuta of S. crefa and tuberculatum, in the umbo being seated in a 

 nearly middle point of the occludent margin, and likewise in the two ridges running from 

 the umbo to the baso-lateral angle, and to a central point of the basal margin ; in which 

 latter character of the ridges, this species also agrees vdth S. semiporcatum. These facts 

 have determined me, provisionally, to rank the present species under Scalpellum. But on 

 the other hand, if we look to the carina, which, according to our rule, is considered the 

 characteristic valve in this genus, it rather resembles the homologous valve in Pollicipes ; 

 for the carina has not any parieties separated from the tectum by a distinct ridge. The 

 terga seldom afford any serviceable generic characters ; but as far as they go, they also 

 rather resemble the terga in Pollicipes than in Scalpellum. Hence, it is obvious, that the 

 generic position of S. (?) cj-eta is at present very uncertain. 



Valves small, smooth, extremely thin and brittle. 



Scutum (fig. 11, c); trapezoidal, with the upper part of the valve produced into a sharp 

 point, and with the rostral angle slightly and obliquely cut off. Umbo seated at a little 

 above the middle of the occludent margin, which is straight. The tergal margin is longer 

 than the lateral margin : the basal margin (on the carinal side of the truncated rostral end) 

 forms a right angle both with the lateral and occludent margins. Valve somewhat convex 

 near to the umbo, whence three obscure ridges radiate, — one to the angle between the tergal 

 and lateral margins ; a second to the baso-lateral angle, and a third to the bend in the basal 

 margin ; these ridges, however, seem to vary in strength, and in the largest specimens 

 could hardly be distinguished : in most of the specimens, the narrow portion of the valve 

 which ends in the truncated rostral angle, is a little inflected. The lines of growth follow 

 the basal and tergo-lateral margins, and can be traced just bending round the sharp 

 apex, so that a very narrow ledge is added along the upper part of the occludent margin. 



Tergum (fig. 21, «) ; sub-rhomboidal, nearly flat : the carinal margin consists of an 

 upper larger portion, and of a lower, shorter portion : the occludent and scutal margins 

 are nearly equal in length. The apex is a little curled towards the scuta, and is sharp ; 

 basal angle bluntly pointed. A faint curved ridge runs from the apex to the basal angle, 

 at about one fourth of the entire width of the valve from the carinal margin. 



The Carina (fig. 11, i^) widens rapidly downwards from the extremely sharp apex; 

 basal margin spear-shaped, sharply pointed, the two edges meeting each other at about an 

 angle of 75°; exterior surface sub-carinated; in a transverse hue the valve is slightly arched, 

 and longitudinally, very shghtly bowed inwards : with a lens, traces of longitudinal striae 

 are visible. 



Dimensions. The species seems to have been always small : the largest scutum and 

 tergura were each about a quarter of an inch in length. Probably the individuals were 

 attached in groups to corallines at the bottom of the cretaceous sea. 



