284 BALANID^. 



difference in outline in the scuta and terga, more especially 

 the greater length of the spur, I conceive I am right in 

 ranking this form as a distinct species, though assuredly 

 it is very closely allied to B. allium, and even still closer to 

 the following B. quadrivittatus. 



36. Balanus quadrivittatus. PI. 8, fig. 1. 



Shell steeply conical, having four longitudinal gray bands 



placed crosswise : radii with their summits oblique : basis 



thin, solid. Scutum, with the lines of groivth smooth; no 



distinct pit for the lateral depressor muscle : tergum as in 



B. cepa. 



Hab. — East Indian Archipelago, attached to lamelliferous corals, and asso- 

 ciated with Pyrgoma grande and Creasia spinulosa, Mus. Brit, and Stutchbury 

 and Darwin. Philippine Archipelago, attached to a Tetraclita, Mus. Cuming. 



I have seen four sets of specimens of this species, taken 

 in four different places, one set containing above twenty 

 individuals, and all resembled each other exactly : never- 

 theless, this species comes so close to B. cepa, that I am 

 somewhat doubtful about its specific distinctness. 



General Appearance. — Shell smooth, or slightly folded, steeply 

 conical; white, with four longitudinal bands of pale brownish-gray 

 colour, namely, on the rostrum, the carina, and the two lateral com- 

 partments : the carino-lateral compartments are very narrow and almost 

 white : the four brownish-gray bands are darkest in the upper part of 

 the shell, though always rather faint, and die out towards the base : 

 thev can sometimes be seen to be formed of several narrow longitudinal 

 stripes ; the tint shows a trace of containing purple. The orifice of 

 the shell is small, rhomboidal, and not quite entire, owing to the 

 obliquity of the summits of the moderately broad radii. In structure, 

 the shell, radii, and alae resemble those in the last species. The 

 basis, however, does not appear to be permeated by pores. Basal 

 diameter of largest specimen *25 of an inch. 



The Scuta most closely resemble those of B. cepa, but the lines of 

 growth are not crenated, and internally there is only a very minute pit 

 for the lateral depressor muscle, placed almost on the edge itself of the 

 valve. r |Jie Tergum hardly differs at all from that of B. cepa, but is 

 perhaps of rather greater breadth. 



The Mouth does not differ from that in the last two species. In the 

 Cirri, the three posterior pairs have elongated segments, bearing only 



