BALANUS. 81 



Parietes : the longitudinal ribs on the internal surface are either feebly, or, in the 

 lower part, strongly developed ; their basal ends are only just perceptibly denticulated. As 

 already stated, in about half the specimens, there were no traces of parietal pores ; in the 

 other half there were either distinct or obscure pores ; the pores are circular, generally of 

 unequal sizes, and never large ; in the same individual they would sometimes be almost 

 wholly absent in some of the compartments, and quite plain in the other compartments. 

 The radii are either moderately wide or rather narrow, and have their upper margins very 

 oblique, and not distinctly arched, and not quite smooth : their sutural edges are very 

 finely crenated, the teeth or septa not being denticulated. The upper margins of the alee 

 are rather less oblique than those of the radii : their sutural edges are barely crenated. 

 The basis is thin, and without any trace of pores ; the upper surface is sometimes furrowed 

 in radiating lines. 



1.1. Balanus inclusus. Tab. II, fig. 5a — bg. 



B. nee parietibus, nee radiis ports perforates ,• basi poris perforata : testa rufo-fuscd .- 

 radiis latis, marginibus superioribus aut non obliquis aut modice ; aciebus suturalibus cum 

 septis plane denticulatis : scuto sine adductoris crista: tergi calcare subangusto. 



Neither walls nor radii permeated by pores ; basis porose ; shell reddish- brown ; radii 

 broad, with their upper margins not oblique, or only moderately oblique ; sutural edges 

 with plainly denticulated septa : scutum without an adductor ridge ; tergum with the spur 

 rather narrow. 



Far. (a) (fig. 5c, 5d), with the shell elongated in its rostro-carinal axis ; basis narrow, 

 clasping the stem of a zoophyte ; lateral compartments much broader than the almost linear 

 rostrum, carina, and carino-lateral compartments. 



Var. {b), with rough longitudinally folded walls, and with the summits of the radii forming 

 an angle of about 45° with the basis. 



Fossil in Coralline Crag; Sutton and Gedgrave ; attached to foliaceous Bryozoa ; Mus. S. Wood, 

 Bowerbank. Var. a, Coralline Crag, Sutton, attached to cylindrical branches of corals ; Mus. S. Wood, 

 Bowerbank. Var. b, attached to shells, Osnabruck, Hanover, Mus. Lyell ; Bunde, Westphalia, Mus. 

 Krantz. 



My materials consist of a beautiful series of specimens in Messrs. Wood and Bower- 

 bank's collections ; but unfortunately only a single young specimen had its opercular valves 

 preserved. Not one specimen of the very curious variety (a) had opercular valves, yet I 

 cannot feel any doubt about its being only a variety, caused by its attachment to a thin 

 cylindrical branch of a coral, instead of to a foliaceous Bryozoon ; it will, however, be con- 

 venient to give a separate description of this very remarkable form. With respect to 

 var. (b), both sets of specimens came to me from the Continent, with the name of 



