296 BALANID.E. 



half as wide as the valve : it is considerably longer, depending beneath 

 the basi-scutal angle more than half its own width : the basal margin 

 of the valve on the carinal side, does not slope so gradually into the 

 spur: the occludent and carinal margins are slightly arched, as in 

 B. bisidcatus. Internally, the surface is rough, the articular ridge is 

 prominent, and the crests for the tergal depressores are well developed, 

 — all as in D. bisidcatus. It is remarkable, how generally the opercular 

 valves have been preserved in this species in its fossil condition, as 

 compared with most other species of the genus. 



It is not easy to distinguish by external characters the 

 rugged varieties of this species from B. crenatus ; indeed, 

 the only difference is that the furrows receiving the edges of 

 the radii, generally, exhibit in B. crenatus a slight impres- 

 sion of the septa, which are entirely absent in B. dolosus. 

 By internal characters, such as the non-porose parietes, and 

 porose basis, our present species widely differs from B. 

 crenatus. 



43. Balanus unguiformis. PL 8, fig. 8 a — 8 b. 



Balanus unguiformis. /. de C. Soicerby (!) Mineral Conchology 



(sine descriptione) Tab. G48, fig. 1, 

 (Jan. 1846). 



— ekisma. /. de C. Soicerby (!) lb., fig. 2. 



— perplexus. Nyst, apud D'Omalius (Sine descript. vel 



Tab.), Geologie de la Belgique, 1853* 



JParietes thin, sometimes permeated by pores ; radii with 

 their upper margins oblique ; sutural edges very finely cre- 

 nated : basis solid. Tergum with the spur narroiv, bluntly 

 pointed. 



Var. erisma, with the walls longitudinally folded or ribbed. 



Fossil in the Eocene formation, Isle of Wight, Colwell Bay ; Hordwell ; 

 Barton, (Chama Bed) ; Hcadon ; Bembridge. Bergh, near Klein Spauwen, 

 Belgium (?). Attached to various shells aud wood. Mus. J. de C. Sowerby, 

 E. Eorbes, F. Edwards, Charlsworth, T. Wright, Bowerbank, Teunant, Bosquet. 



* I am much indebted to M. Bosquet for specimens bearing this title, from 

 Klein Spauwen, which certainly appear to me, as far as can be judged by the 

 separated compartments, without the opercular valves, to belong to our 

 present species. 



