20 CONCHOLOGY. 



B. ovularis. B. subimbricatus. 



B. miser. B. rugosus. 



B. amphimorphus. B. placianus. 



B. perforatus. B. crispatus. 



B. laevis. B. punctatus. 



B. spinosus. B, fistulosus. 



B. radiatus. B. latus. 



B. sulcatus. The furrowed Balanus. 

 White ; valves nearly smooth ; operculum strongly ridged 

 transversely, with longitudinal, nearly obsolete striae. 



B. tintinnahulum. The little Bell Balanus. PI. 4, fig. 1. 

 Shell conical ; valves strongly and irregularly ribbed ; in- 

 terstices delicately striated transversely ; colour purple. 



B. spinosus. The spiny Balanus. 

 Either has no support or a membranous one ; armed with 

 spines exteriorly. 



4. Acasta. Three species. 

 Found in sponge, from which, when detached, it cannot 

 stand erect on account of the convexity of the base. 



Shell oval, subconic, shaped like a Patella, with six lat- 

 eral unequal valves slightly connected ; operculum with four 

 valves. 



Acasta Montagui. Acasta glans. 



A. sulcata. 



A. Montagui. Montague's Acasta. 

 Valves erect, triangular, acute, with muricated ascending 

 spines. 



5. Creusia. Three species. 



The shells of this genus are generally small ; found in 

 the seas of hot countries attached to madrepore and other 

 marine substances. 



Shell sessile, thin, Patella-shaped ; aperture oval, rather 

 large, closed by a large sub-pyramidal bivalve operculum ; a 



