_Structure of the shell and basis._--The parietes are permeated by quite distinct pores,--a character sufficient by itself to separate this from the following species; the longitudinal septa forming the tubes are slightly denticulated at their bases. The radii have their summits quite square, extending from apex to apex of the adjoining compartments. The alæ have oblique summits. The sutural edges of the radii have approximate septa, which are obscurely denticulated: the interspaces are filled up solidly, so that the radii are not porose. The basis is distinctly porose, by which this species can be distinguished from _B. navicula_ and _cymbiformis_. The basis has a deep furrow on the under side, from clasping the thin horny axis of the Gorgonia: the basal point of the rostrum is also notched from the same cause, and, as a consequence, its upper surface becomes slightly furrowed along its whole length. The _Scuta_ have an articular ridge but moderately prominent, and only slightly reflexed; the basi-tergal corner is rounded off; there is no adductor ridge; there is a small, rather deep, distinct pit for the lateral depressor muscle. _Terga_; externally the surface is considerably depressed in the line of the spur. The spur is between half and one-third of the width of the valve: its lower end is square and truncated, or in some degree rounded; it is sometimes (3 _e_) dentated with a few, minute, sharp teeth. The articular ridge is but slightly developed; the crests for the depressor muscle are very feeble. _Animal's body_ unknown. 11. BALANUS GALEATUS. Pl. 3, fig. 4 _a_-4 _c_. LEPAS GALEATA (?) _Linnæus._ Mantissa altera Holmiæ, 1771. CONOPEA ELONGATA. _Say._[90] Journal of Acad. Nat. Sci. Philadelphia, vol. ii, part 2, p. 323, 1822. [90] If I have assigned the specific title of _galeatus_ to the wrong species, yet Say's name of _elongatus_ ought not strictly to be admitted; as the _Lepas elongata_ of Gmelin is a Balanus,--probably a variety of _Balanus crenatus_. I may add, that as the _Lepas galeata_ of Schröter ('Einleitung in die Conch.' &c.), was attached to a Gorgonia from the East Indies, it cannot be our present species, but probably is one of the three other allied species, which all occur in India. _Parietes not porose; basis porose. Tergum, with the apex square, caused by the great development of the articular ridge._ _Hab._--Charlestown, South Carolina; Florida; West Indies; Central America; attached to Gorgoniæ; Mus. Brit., Agassiz, Cuming, Stutchbury.