190 
Stat. 310. February 12, 1900. Lat. 8° 30'S., Long. 119°7.5 E. Depth 73 m. Bottom: sand 
with few pieces of dead coral. Half a dozen small specimens, some of them 
attached to the shell of a Lamellibranch (Avzcu/a), others to a Bryozoan (like 
Halodactylus), others to a species of sponge. 
General Remarks. This seems to be a rather common species at the places where 
it occurs. It doubtless belongs to the group of species of which B. amaryllis is the best known. 
9. Balanus tenuis Hoek. Pl. XVII, fig. 14—r19. Pl. XVII, fig. 1. 
Hoek, P. P. C., Report on the Cirripedia of the Challenger Expedition, 1883, p. 154, pl. XIII, 
fig. 29—33. 
This species also belongs to the group of species with narrow radii, striated scuta, terga 
with the scutal margin hollowed out and relatively broad spur. When describing the species 
as a new one (1883), I pointed out that it corresponds in several details to B. amaryllis. 
Several other new species of the same group were collected during the cruise of the Siboga. 
A pale-red-coloured specimen of considerable size was brought up with the dredge from 
a coral bottom and a depth of 275 m. It is an incomplete specimen, without opercular 
valves, and it broke into pieces before I had sufficiently investigated it. A small specimen of the 
same colour and with valves of corresponding shape, was found attached to one of the com- 
partments of the larger specimen (PI. XVII, fig. 14). The latter belongs no doubt to the 
same species. 
The shell is conical, its orifice medium-sized, and distinctly toothed. The radii are extre- 
mely narrow, with their summits very oblique, in the smaller specimen visible only along inferior 
half of valves. The alae are considerably broader, wih their sumttmis rounded. The compart- 
ments are furnished on the inner surface with vertical ridges, which increase in size and strength 
towards the basis. Neither compartments nor radii have pores. Of the larger specimen the basis 
is wanting; the smaller one has a delicate calcareous basis, with ridges radiating from the centre. 
I could not see any canals in the basis, The diameter of the smaller specimen is 7.5 mm. near 
the basis, its height 4.5 mm.; the highest compartment of the larger specimen measures 32 mm. 
The scutum (Pl. XVI, fig. 15@ and @) is delicately but distinctly striated longitudi- 
nally. The inner surface is roughened on the upper part, the adductor ridge is feebly deve- 
loped, the articular ridge is rather prominent, and extends over half the length of the tergal 
margin; the tergum (Pl. XVI, fig. 15, 6 and @) has the scutal margin only slightly hollowed 
out, the spur is rather broad, and extends to a distance from the basi-scutal angle, which is 
not greater than its own width. The valve is slightly beaked. Studying it with a strong lens, a 
trace of longitudinal striation is seen at the surface. 
The description I gave of the animal’s body in the Report on the Challenger-Cirripedia 
can be completed with the following remarks: : 
Mouth. Labrum (PI. XVII, fig. 16) with the central notch shallow, wide at entrance, 
the three teeth on each side close together, the height of the sub-triangular shield-like portion 
about three-fourths of its breadth. 
Palpi slightly elongate, with the upper margin nearly straight, and the basal margin 
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