BALANUS. 29 
radiating ridges: the septa between the radiating pores are themselves often in part porose, 
as was plainly the case in the specimen (fig. 34) engraved. The orifice of the shell is 
large and elongated in its rostro-carinal axis, especially in young specimens. ‘The basal 
diameter of the largest specimen is °4 of an inch. 
The scuta (fig. 3c) have no trace of the two or three longitudinal furrows so con- 
spicuous on these valves in B. diswlcatus, and which, in that species, run down to the basal 
margin from the apex of the valve, this fact showing that the furrows occur in quite young 
individuals. The whole valve is not quite so narrow as in B. disulcatus, but otherwise 
agrees with it in shape: internally, there is hardly any difference ; but the articular furrow is 
not quite so wide: the articular ridge is very prominent, and abruptly truncated at its lower 
end: the adductor ridge is also prominent; it here runs a little higher up the valve than 
in B. disulcatus. The tergum (fig. 8d) differs more in the two species: the spur is not so 
broad; measured in its upper part, it is only about one third of the entire width of the 
valve, instead of being 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. disulcatus. Internally, the surface is rough, the 
articular ridge is prominent, and the crests for the tergal depressores are well developed,— 
all as in B. disulcatus. 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 slight impressions 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. 
10. Bauanus unevirormis. ‘Tab. II, fig. 4a—4/. 
BaLanvs uncuirormis. J. de C. Sowerby (!) Mineral Conchology (sine descriptione), 
Tab. 648, fig. 1, (Jan. 1846.) 
—  rRisMA. J. de C. Sowerby (!)  Ib., fig. 2. 
—  PERPLEXUS. WNyst, apud D’Omalius (sine descript. vel Tab.), Géologie de la 
Belgique, 1853.1 
B. parvetibus tenuibus, interdum poris perforatis: radiis sine poris, marginibus su- 
perioribus obliqms ; aciebus suturalibus tenuissimé crenatis: basi sine poris: tergi calcare 
angusto, obtuso. 
1 J 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. 
