70 
THE VOYAGE OF H.M.S. CHALLENGER. 
diverge abruptly outwards so that the lips appear much prolonged anteriorly. The sides 
of the shell are often prolonged into a more or less projecting point. The embryonic 
shell is not separated by a distinct constriction, except in Cavolinia trispinosa and 
Cavolinia quadridentata. 
The animal somewhat resembles in its external characters the species of Clio strictly 
so called. Its special characters chiefly consist in the breadth of the posterior lobe of 
the foot and in the presence of lateral prolongations of the mantle, which project from 
the lateral portions of the aperture (side clefts of the adult) and may cover a considerable 
portion of the shell. 
Many authors (A. Adams, Gray, Fischer, Boas, &c.) call this genus “ Cavolinia, 
Gioeni,” and do so on the authority of Abildgaard, according to whom Gioeni first used 
this title in his work entitled “ Descrizione di una nuova Famiglia e di un nuovo Genere 
di Testacei trovati nel littorali di Catania.” This small memoir (8vo and not 4to as is 
always noted) is somewhat rare, and does not appear to have been actually seen by the 
authors who cite it from Abildgaard. For in the memoir itself it may be seen that 
while Gioeni has indeed represented Cavolinia tridentata in his figures xiv.-xvi., 
he does not give it its title. Caulini is referred to on p. xxvii, note a, as the first to 
observe the animal of this species, but there is no question of naming in his honour the 
“nuovo Genere di Testacei.” 
The name “ Cavolina” (em. Cavolinia ) only dates from 1791, and its author was 
Abildgaard. It has, nevertheless, the priority over Cavolinia, Bruguiere, which was 
not published till 1792, 1 and ought to be employed in preference to the title Hyalsea, 
Lamarck, 1801. 
Although the shells of Cavolinia have a much constricted aperture, different 
individuals within the same species may exhibit very noteworthy divergences in regard 
to size. The difference is sometimes very striking, so that in some species the diameter 
of certain individuals may be four times that of others ( Cavolinia longirostris, after 
Boas). 2 
From this fact it has been inferred (Pfeffer) 3 that, in order to grow, the shells of 
Cavolinia must first of all lose all the contracted portion by absorption, since growth can 
only take place by the apposition of fresh material at the margin of the aperture. 
But this hypothesis of partial absorption is altogether imaginary. As Boas has 
already pointed out, 4 there is no trace of a line of reabsorption on the shells of large size, 
and it is further a very strong argument against the theory that the posterior (oldest) 
portion of the small individuals does not correspond exactly to the homologous portion 
1 Encyclopedic Methodique ; Histoire naturelle des Vers, t. i. 
2 Spolia atlantica, p. 206. 
3 Die Pteropoden des Hamburger Museums, Abhandl. Naturw. Ver. Hamburg, t. vii. p. 75. 
4 Spolia atlantica, p. 207. 
