164 
course, species in deeper water may as well have developed from such forms: the species of 
Balanus occurring in deeper water (see the table p. 153) do not belong to one and the 
same section and, probably, had a very different descent. 
1. Sectio: Mega-Balanus 
1. Balanus tintinnabulum (Linn.). 
DARWIN, CH., Monograph. Balanidae and Verrucidae. 1854, p. 194, pl. I. fig. a—/, pl. II, fig. 1a—to. 
This species is represented by one sample only: a few specimens, which were found 
attached to the bottom of H. M. S. “Siboga”, when the ship was docked on October 15', 
1899. The ship had been previously docked and cleaned on June 1‘, of the same year: so the 
Balani, probably, developed in the period between the two dates. 
The sample is composed of four specimens that caused me great trouble. One of the 
specimens can be determined at once as belonging to Darwin's variety (3) valedus; but the 
remaining three represent two forms, not only different from the first, but also different from 
all the varieties (11 in all) described by Darwin. Therefore the case mentioned by Darwin in 
which three most distinct varieties were taken from the bottom of the same vessel, is here 
repeated. The three specimens are relatively small, and I do not feel sure, therefore, that they 
are full-grown animals. Their form — of one especially — is so characteristic, that I really prefer 
to describe them as different varieties. 
a. B. tintinnabulum, var. validus Darwin. 
The specimen looks exactly like the figure (PI. I, fig. ¢) given in Darwin’s Monograph. 
The coarsest and strongest specimens that Darwin saw, were said to have been attached to 
a surface of iron: this holds good also for the one taken from the surface of the “Siboga’’; 
parts of the outer surface of the basis are coloured red, from the ship’s being painted with red-lead. 
The shape of the shell is conical, slightly convex at the rostral side; it is coarsely 
ribbed, with some of the ribs flexuous and most of them rugged; the orifice is relatively large, 
rounded, angular, but at the rostral and carinal extremities, the basis is partly lost, the 
remaining part is flat and the whole must have measured 29 and 20 mm. in diameter. The 
tergum corresponds almost exactly to the figure given by Darwin for his variety communis: 
it has a well-developed longitudinal furrow, which is quite closed, a prominent articular ridge, 
extending over three fourths of the length of the valve, the spur is produced for a con- 
siderable distance up the internal surface of the valve, the crests for the depressor muscle 
are only feebly developed. The scutum has rather prominent lines of growth, the general 
shape resembling that of Darwin’s var. coccofoma. The articular ridge is broad, much reflexed 
and slightly hooked at its base, it extends over half the length of the valve. The adductor 
ridge is well-developed and the cavity for the lateral depressor muscle rather deep. 
Darwin did not say where his specimens of this variety were collected. We now know 
for certain that it occurs in the Malay Archipelago. 
36 
