1910.] N. ANNANDALE: Barnacles of the subgenus Smilium. 149 
in the development of the females or hermaphrodites of many 
species in which these six valves are at any rate very much more 
conspicuous than any others, it they are not actually the only 
valves represented. Incompleteness, however, is much more 
common in the subgenus Scalfellum, if it is not actually confined 
to that subgenus, for species like Scalpellum (Smilium) scorpio, in 
which the valves are embedded in very thick membrane, do not 
exhibit incompleteness in the sense in which I have defined the 
term. 
In the young hermaphrodites or females of those species of 
Scalpellum in which incompleteness occurs, at the stage at which 
all the valves have already made their appearance, the valves are 
practically normal, and it is only as maturity approaches that 
their margins become strongly excavated. 
As regards variation in the development of the valves one 
other point may be noted, viz., the rudimentary character of the 
subcarina and the rostrum in some otherwise normal individuals of 
species in which they are habitually present. These two valves 
are rightly considered to be of great importance in the taxo- 
nomy of the genus, but it must be noted that even in some spe- 
cies of Smilium (e.g., S. squamuliferum, otherwise a very constant 
species) the subcarina is often very minute andstill more often 
completely concealed beneath the membrane. In some species of 
the subgenus Scalpellum, on the other hand, the rostrum. which 
is always small, may be present or absent, and even the subcarina, 
which is normally absent in this subgenus, occurs as a minute 
rudiment in some individuals of S. laccadivicum, of which my S. 
subflavum is evidently no more than a ‘‘ complete’”’ variety. 
SUBDIVISION OF THE GENUS SCALPELLUM. 
Considerable difference of opinion has been held at different 
times, and, indeed, is still held, by different authorities as regards 
the subdivision of the genus Sca/pellum (sensu Darwinio). Darwin’s 
great work must be taken as the foundation of all scientific study 
of the Cirripedia, but it must be remembered that he was only 
acquainted with a very small proportion of the species of Scalpel- 
lum now known, and that even as regards the few species he had 
examined he did not express a dogmatic opinion. Before he wrote 
his Monograph (1851) Gray and other authors had already des- 
cribed several genera wholly or in part synonymous with the forms 
he called Scalpellum. Pilsbry! has recently (1908) revived two of 
these genera, namely, Calantica and Smilium, and has also raised 
several other groups in the genus to generic or subgeneric rank, 
basing his conclusions partly on the external form of the dwarf 
male and partly on the position or presence of certain valves in 
the female or hermaphrodite. Hoek and Gruvel, on the other hand, 
_! “On the classification of Scalpelliform Barnacles,’’ Proc. Acad. Nat. Sct. 
Philadelphia, 1908, p. 104. 
