HUDSON RIVER BEDS NEAR ALBANY 579 



numbers of individuals that, Darwin writes, one could call the 

 present age that of the cirripeds, in all the time from the Devonic 

 to the Upper Jurassic. The long suppression of the mammals in 

 Mesozoic time and their sudden rise at the beginning of the 

 Cenozoic time seems to be an analogous case from the terrestrial 

 fauna. 



The valves have been tentatively described by terms of such 

 valves of P o 1 1 i c i p e s and Scalpellum as they most 

 resemble, with which it is not so much intended to assert their 

 actual homology as to designate them by names, and to emphasize 

 their great similarity to the parts of the capitula referred to. 



1 Tergum. Convex, elongate subrhomboidal to subtrian- 

 gular, as the upper and lower carinal margins blend into each 

 other. Carinal margin the longest, rounded; scutal margin 

 gently rounded, about twice as long as the occludent margin. 

 Occludent margin and upper part of carinal margin meet at an 

 angle of over 45°, occludent and scutal margins at about 135°. 

 From the apex to the sharp basal angle, a strongly projecting, 

 angular, strongly curved conspicuous ridge runs at about one 

 fourth of the entire width of the valve from the carinal margin; 

 the surface slopes,apparently on account of lateral compression, 

 much steeper away on the carinal side. A wide depression with 

 a central, broad but low, slightly curved ridge extends from the 

 apex to the middle of the scutal margin. 



The surface is covered with unequal, somewhat lamellose 

 growth lines, running parallel to the base of the valve. Where 

 the shell has become exfoliated, regular rows of pustules running 

 parallel to the keel become visible. These probably represent a 

 system of pores within the corium. 



It is specially this valve that, in its outline, diagonal keel, 

 direction of growth lines and curved fold on the larger face, fully 

 agrees with the terga of some species of Pollicipes. 



2 Carina. Lanceolate fragments are thought to have been 

 part of the carina. The fragment figured apparently had two 

 equal wings and a median, highly prominent, angular keel (an- 



