(sect, d.), balanus glanuula. 265 



from Canada. There are well-characterised specimens in the mamma- 

 liferous Crag, at Bramerton and near Norwich, in Sir C. Lyell's col- 

 lection, and from Sutton and other places in the Red Crag of the 

 eastern shores of England : these specimens are decidedly not only 

 smaller than the glacial, but than the recent English specimens ; for 

 the largest Crag specimens which I have seen had a basal diameter of 

 only 'o5 of an inch. The specimens which I have seen from the Coral- 

 line Crag, and some others sent me by Krantz from themiocence for- 

 mation of Flonheim bei Abzei, in Germany, had not their opercular 

 valves, yet I cannot doubt, considering how few species there are in the 

 present section of the genus, that I have rightly identified them. 



Diagnosis. — Under the head of B. balanoides I shall make a few re- 

 marks on the diagnosis between that and the present species; as B. im- 

 provisos is found on the British shores, sometimes mingled with B. 

 crenatits, I may observe that, externally, the only difference consists in 

 the edges of the radii in B. improvisus being much smoother and 

 rounded, and in the whole shell being less rugged. Internally, in B. 

 improvisus the porose basis, the presence of an adductor ridge on the 

 under side of the scutum, the graduated teeth on each side of the central 

 notch in the labrum, and the little inequality in length of the rami of 

 the first pair of cirri, are clearly and amply diagnostic. 



28. Balanus glandtjla. PI. 7, fig. 1 a, 1 b. 



Shell white ; parietes with the internal lamina generally 

 strongly ribbed longitudinally, with the pores imperfect 

 and small, sometimes in part absent ; radii narroio, with 

 their summits rounded. Scutum with an adductor ridge ; 

 tergum with the spur truncated and rounded. 



Habitat. — California, Mus. Cuming, Aug. Gould ; attached to shells and 

 wood, together with B. nubilus. Southern Pacific ocean, attached to Pollicipes 

 polymer us, Mus. Brit. 



General Appearance. — Shell steeply conical, or cylindrical and 

 elongated ; dirty white ; walls rugged, longitudinally folded ; radii 

 narrow, with their summits very oblique and rounded ; orifice toothed. 

 Basal diameter of largest specimen half an inch. 



Scat inn, resembling externally that of B. crenatus ; rather broad, 

 surface smooth ; articular ridge very prominent, and articular furrow 

 very wide ; hence, when the summits of the opercular valves are worn 

 down, the two scuta together form a square projection indenting the 

 two terga, as in B. balanoides. Internally, there is a small adductor 

 ridge, on the lower side of which there is a pit, as if for a muscle. The 

 depression for the lateral depressor muscle is small, but variable. 

 Tergum without any longitudinal furrow, and hardly a depression : spur 



