19S Mr. T. H. Withers on some 



Description. — Rostrum (PI. VIII. fig. 11) siibtri angular, 

 basal margin acutely rounded, breadth almost equalliug the 

 leugth, strougly convex transversely, with the apical portion 

 moderately incurved, and a wide, but not very prominent, 

 rouuded, mediau ridge extending from the apex to the basal 

 margin. On the inner surface a gently rounded, delicate 

 ridge extends from the lateral angles to a point nearly one- 

 third the length of the valve from the apex ; the portion of 

 the valve above this ridge must have projected freely, but 

 it is not perceptibly thickened, and the growth-lines are not 

 apparent. 



Structu?'e and Affinities of Scillselepas dorsata 

 and S. valida. 



So long as the species Pollicipes dorsatus and P. validus 

 of Steenstrup were known only by the disconnected valves 



Fiff. 1. 



r. 



C<dantica {Scillalepas) dorsata, Ste^nstrup, pp. Daniau : Faxe, 

 Denmark. Restoration of capitulura. 



c, carina ; c.l., carinal latus ; m.L, median latus : r., rostrum ; 

 r.l., rostral latus ; s., scutum ; s.c, subcarina ; t., tergum. 



of the upper whorl, it was an open question whether they 

 should or should not be referred to the group of species 

 included under Scillce/epas, although these valves approached 

 more closely to the species of Sci/ialepas than to those of 

 Pollicipes. Dr. K. Briiunich Nielsen^s discovery, however, 

 of a number of valves of the lower whorl of P. dorsatns in 

 the Danian of Faxe, Denmark, includiug those here figured 

 (PL VIII. figs. 16-21), enables us not only to prove that the 

 species is a true Scilkelepas, but also to give a restoration of 

 the capitulum (see text-fig. 1). The capitulum is formed 

 of a cariua, paired scuta, and paired terga, w ith three pairs of 



