Hab.—Columbia River, west coast of North America, Mus. Brit. and Cuming; Behring Straits (Capt. Kellett); the Kurile Islands, according to Pallas. Attached to shells, and to each other in groups.
General Appearance.—Shell steeply conical, with a rather small oval orifice; or cylindrical, with a large rhomboidal and little toothed orifice. Colour dirty white. Surface either simply rugged, or more commonly covered by numerous, narrow, extremely prominent, longitudinal plaits; from the manner in which these overlap each other, the shell almost appears as if thatched with straw. The upper corroded part of the shell usually exhibits a cancellated and finely punctured surface. The radii are generally very narrow, forming towards the base of the shell a mere narrow ribbon to each compartment, and often hardly distinguishable; but in one specimen they were of considerable width: in the former case, the alæ are often widely exposed. The largest specimen which I have seen was 1.5 of an inch in basal diameter, but Pallas gives 2.2 as the measurement of a specimen from the Kurile Islands.
The opercular valves are united to each other and to the shell by unusually strong membrane; and the upper parts of both valves, in all the specimens seen by me, have been much disintegrated. The Scutum, in old specimens, is faintly striated longitudinally, but in some there is hardly a trace of this: the occludent margin is furnished with a few large knobs, not corresponding with every alternate line of growth (as is usual with other species), but with every fourth or fifth line. Internally, the articular ridge is moderately prominent (in young specimens more prominent) and reflexed. The adductor ridge is sharp and prominent; in the upper part it is confluent with the articular ridge, but in young specimens can be seen to be distinct; in the lower part it borders a large deep cavity for the lateral depressor muscle, in the middle of which there is a very slight longitudinal ridge; this cavity sometimes is almost closed or arched over in its upper part. In one specimen, the basal margin of the scutum was deeply hollowed out in the middle. The Tergum is remarkably narrow, with its apex produced into a triangular beak, hollow within, and sometimes faintly tinged purple. A deep, closed, longitudinal furrow runs down the valve. The spur is long, remarkably narrow, and pointed. Internally, the spur is produced up the valve as a ridge: the inflected scutal margin, and the prominent articular ridge, are both nearly straight, and parallel to the spur. The crests for the depressores are sharp and very prominent.
The Parietes are very thick and strong: unlike every other species of the genus, they consist of several very irregular rows, of unequally sized, round or angular tubes ([3 b]). These tubes or pores are generally short, and are at frequent intervals crossed by transverse septa; they often rather deserve to be called cells than tubes. New tubes are formed along the inner as well as along the outer lamina. They are lined by dusky purple corium. The internal surface of the parietes is smooth in the upper part, and in the lower, it is reticulated by slight, irregularly branching ridges. The carinal internal margin of each compartment projects a little, as in the case of [B. crenatus] and [balanoides]. The lower edge of the sheath is either hollow beneath, or is united to the walls. The radii in one specimen were broad, with slightly oblique, jagged summits; generally they are extremely narrow, forming more ribbons along the lower edges of the compartments, barely extending up as high as the sheath. They can sometimes hardly, or not at all, be seen, until the shell is disarticulated: in rather young specimens the sutural edge is sometimes quite smooth; in old specimens the lower part of the edge has coarse arborescent septa, with the interspaces filled up solidly, whilst the upper part is smooth. The alæ are conspicuous from the outside, owing to the little development of the radii; but owing to the diametric growth not having been great, the part added during such growth is narrow; the summits of the alæ are only slightly oblique: the sutural edge is coarsely crenated, with the teeth denticulated or slightly arborescent.
Basis membranous.
Mouth: labrum with only four very minute teeth: mandibles with four teeth; the third tooth broader than the first; the fourth small. Maxillæ, with the two upper spines placed on a slight prominence, beneath which there is a small notch. Cirri of a very dark colour (much injured): the segments of the first, second, and third pairs very broad and short, protuberant in front, and most thickly clothed with spines; the third pair is very little longer than the second pair: the sixth pair (in a large specimen above one inch in basal diameter) had the segments broader than long, each furnished with seven pairs of spines.
Affinities.—This species, though very distinct, evidently comes near to [B. balanoides], especially to var. (a). By merely doubling or trebling the irregular rows of short tubes in the walls of [B. balanoides], with their reticulated inner lamina and longitudinally folded outer lamina, we should have the structure exhibited in [B. cariosus]. We have seen, also, that in var. (a) of [B. balanoides], the spur of the tergum is remarkably sharp, as in [B. cariosus]. This species, also, in a very marked manner approaches in many characters, especially in the opercular valves, in the cirri, and to a certain extent in the shell and basis, to [B. flosculus], and even in external appearance to var. sordidus of the latter—an inhabitant of the opposite extremity of the continent, namely, of Tierra del Fuego. Again, the tergum to a certain extent, and the scutum in a singular manner, resemble these valves in [B. nubilus], showing an unequivocal affinity to that species. With respect to the most remarkable character of the species, namely, the several irregular rows of tubes or pores in the walls, it deserves notice that in [B. crenatus], which is certainly closely allied to [B. balanoides], the longitudinal septa sometimes divide near the outer lamina, thus giving rise to a few additional tubes. Of the above several species, to which our present species is allied, [B. flosculus] stands in the next section, and [B. nubilus] and [crenatus] in the last: hence we see that [B. cariosus] has singularly divergent affinities. The peculiar structure of the parietes, together with the general appearance of the shell, made me at the first moment suppose I was examining a [Tetraclita] (or Conia of Leach); hence, also, it has arisen, that Lepas cariosa of Pallas has often been quite erroneously given as a synonym of [Tetraclita porosa].
31. [BALANUS] DECLIVIS. Pl. [7], fig. [4 a]-[4 d].
Parietes solid; rostrum nearly twice as long as the carina or carino-lateral compartments, hence the basis is oblique. Tergum with the spur truncated, half as wide as the valve.