286 BALANID.E. 



duced into long spikes, corresponding with those on the basal margin of 

 the parietes : these projections equal half the semi-diameter of the shell. 

 The internal surface of the basis has slightly prominent, rounded ridges ; 

 and the external surface has extraordinarily prominent, sharp ridges, 

 radiating from the centre ; the edges of the external ridges are irregular, 

 notched, and knobbed. I have seen in no other species external 

 ridges on the basis or surface of attachment ; and what is more re- 

 markable, the interspaces between the ridges are penetrated by small 

 rounded apertures, of irregular shape and unequal sizes ; and these are 

 generally arranged in an irregular' double row, and externally are closed 

 by the membrane, which clothes the basis. In the sub-genus Acasta, 

 the basal cup is sometimes penetrated by similar holes, but these seem 

 never to extend over the whole basis, and are very variable ; neverthe- 

 less, in some specimens of Acasta spongites from the Cape of Good 

 Hope, portions of the basis closely resembled, except in the absence of 

 the radiating ridges, the structure here described, but the holes were 

 not arranged in any definite order. The internal surface of the 

 parietes in Acasta sporillus presents a somewhat analogous appearance, 

 but the pits do not penetrate through the walls. This species, I have 

 no doubt, is closely allied to the sub-genus Acasta, and to Balanus 

 navicula with its allies, and, but much less closely, to B. allium with 

 its allies. Indeed, had B. terebratus inhabited a sponge, 1 should 

 have been compelled to have ranked it in the sub-genus Acasta. 



38. Balanus vestitus. PI. 8, fig. 3 a — 3 b. 



Shell pinkish-purple or white, clothed by an orange-coloured 

 membrane ; radii represented by mere fissures ; basis solid. 

 Scutum, with a sharp, curved adductor ridge; with crests for 

 the lateral deptressor muscle : tergum, with the spur short, 

 truncated, one third of toidth of valve. 



Hab. — New Zealand, New South Wales, Mus. Brit, and Stutchbury ; attached 

 to shells. 



General Appearance. — Shape conical, often steeply conical ; orifice 

 small ; radii not developed, represented by mere fissures. The walls 

 are smooth, or slightly, or strongly ribbed longitudinally. The shell 

 itself is of a fine peach-blossom pink, or nearly white, but it is 

 generally covered by a thick yellow or brownish-orange epidermis. 

 Opercular valves pinkish, but similarly covered. Basal diameter of 

 largest specimen ■ 7 of an inch. 



Scuta, with the lines of growth closely approximate ; surface some- 

 what convex. Internally, the articular ridge is very little prominent, 

 but runs far down the tergal margin ; in some specimens, however, it 

 is shorter and more prominent. The adductor ridge is strongly pro- 

 minent, is curved towards the rostral angle, and runs down nearly to 



