30 FOSSIL CiRRIPEDIA. 
Parietes thin, sometimes permeated by pores; radii without pores, with thew upper 
margins oblique; sutural edges very finely crenated ; basis without pores. Tergum with 
the spur narrow, bluntly pointed. 
Var. evisma (fig. 40), with the walls longitudinally folded or ribbed. 
Fossil in the Eocene formations, Isle of Wight, Colwell Bay ; Hordwell; Barton, (Chama Bed) ; Headon ; 
Bembridge ; Bergh, near Klein Spauwen, Belgium (?). Attached to various shells and wood. Mus J. de 
C. Sowerby, E. Forbes, F. Edwards, Charlsworth, T. Wright, Bowerbank, Tennant, Bosquet. 
This species, the most ancient one as yet well known in the genus, presents to the 
systematist a most unfortunate peculiarity, in the parietes being almost as often as not 
permeated by small pores: Ihave seen no other instance, except to a limited degree in the 
recent B. glandula, of this character being variable, and hence it must be still considered 
of high classificatory value, im so varying a genus as Balanus. Owing to the kindness of 
Mr. F. Edwards, I have seen the original specimens, excellently figured by Mr. J. de C. 
Sowerby, in the ‘ Mineral Conchology,’ under the names of B. unguiformis and erisma, 
between which I can perceive no difference, excepting that the walls in the latter are 
longitudinally folded,—a character we know to be variable in many species. In both 
varieties, the parietes are sometimes porose and sometimes solid. The smaller specimens, 
however, figured in the ‘ Mineral Conchology’ to the right hand of the Plate, may possibly 
be a distinct species, as | infer from the narrowness of their radii. This species is inti- 
mately allied to B. varians, a fossil from the ancient tertiary plains of Patagonia. It is also 
allied to the recent B. crenatus and glandula. 
General appearance.—Shell (fig. 4a), tubulo-conical, sometimes even sub-cylindrical : 
surface either very smooth, or slightly folded, or deeply folded so as be strongly ribbed 
longitudinally: orifice rather large, rhomboidal, narrow at the carinal end, toothed, 
but not deeply: walls rather thin and fragile: radu of moderate width, with their summits 
oblique, not quite smooth. Basal diameter of largest specimen about three quarters of an 
inch. 
Scuta (fig. 4c), with the external surface smooth: there is a trace of a furrow running 
down the valve from the apex, near to the occludent margin, and this is only worth 
mentioning from the analogous furrows in B. disculatus. Internally (fig. 4e), the upper 
surface of the valve is roughened: the articular ridge is very prominent, and slightly 
reflexed: there is no distinct adductor ridge; there is a slight but variable depression for 
the lateral depressor. Zergum (fig. 4d), with the longitudinal furrow shallow; spur 
moderately long, about one fourth or one fifth of the width of the valve; placed at about 
its own width from the basi-scutal angle; basal end bluntly pointed; the basal margin on 
the opposite sides of the spur forms a nearly straight line; the carinal margin has an 
extremely narrow border formed by upturned lines of growth. Internally (fig. 4,f), the 
surface is roughened with little points: the articular ridge is prominent: the crests for the 
tergal depressores moderately prominent. 
