(sect, c), balanus corrugatus. 255 



opercular valves of the two species closely resemble each 

 other. This may be the B. stellaris of Bronn, but it is 

 futile attempting to identify the species of this genus merely 

 by external characters, even when aided, as in this case, by 

 an excellent drawing of the shell. 



General Appearance. — Shell conical, with broad rounded longitudinal 

 folds ; orifice of moderate size, oval ; radii narrow, with their upper 

 margins oblique ; but the summits of both specimens had been much 

 broken. Colour, as it appears, originally white. Basal diameter of 

 largest specimen |- of an inch. 



Scuta, with the upper portion much reflexed ; the articular ridge is 

 very prominent, and the articular furrow of great width ; when the valve 

 is viewed from the outside the articular ridge is very conspicuous: there 

 is no adductor ridge. Terga, with the longitudinal furrow very slight; 

 the spur is from one third to one fourth of the width of the valve, and 

 its basal end is blunt and almost truncated ; it stands about half its own 

 width from the basi-scutal angle. Internally, the articular ridge is very 

 prominent, and the articular furrow narrow and deep, extending down 

 the valve in the line of the spur. 



Parietes : the parietal tubes are remarkably large, and I think this 

 can hardly be an individual peculiarity: the tubes are crossed by many 

 transverse septa, close down to the basis. The radii are narrow, and 

 have jagged, oblique summits : their sutural edges have very distinct 

 septa, barely denticulated, with the interspaces filled up solidly. The 

 alec have oblique summits ; I was unable to make out the structure of 

 their sutural edges. The Basis is very distinctly permeated by pores, 

 which are crossed by transverse septa. 



The shell and opercular valves of B. corrugatus so closely 

 resemble the same parts in B. crenatus, that I should not 

 be much surprised at seeing the two species graduating into 

 each other, if a larger series of specimens, from beds inter- 

 mediate in age between the Sub-Appennine formations and 

 the present time, were obtained. If indeed the basis of 

 B. crenatus were permeated by pores, the tw r o species could 

 hardly be discriminated. 



