222 
carina. It would be of great interest to study the development of this 
peculiar genus in order to see if the carina is not indicated in the 
pupa. — The skeleton of the peduncle is in Ibla represented by 
numerous chitinal spines or hairs, in the adult of one species again 
disappearing. In Ibla males are present and attain a comparatively 
high organisation; the affinity with Protomitella is evident, and no 
heed being paid to the secernation of carbonate of lime, there is 
no great gap here either. 
We shall here have to face the question, whether it is pos- 
sible to give a plausible explanation of the absence of a male in 
Scalpellopsis, Mitella, and Lithotrya, as compared with the other 
genera of this great phylogenetic group. Evidently the biological 
conditions give us a key. Calantica, Smilium, and Scalpellum are 
in general deeper living forms, and the individuals are only seldom 
found living crowded; quite on the contrary, the dredges very 
seldom catch more than one or some very few specimens of one 
species at a time. A cross fertilization would here be almost pre- 
cluded, if no males had been present. Protomitella, and Ibla are 
shallow-water genera; Ibla is a rare genus, the individuals of which 
always seem to occur almost singly. The biology of Protomitella 
demands further study; here the male seems to be about to dis- 
appear, or it is more numerous at some time of the year than at 
others; the only species known does not seem to be very abundant. 
Turning to the other genera we find that Mitella is an inhab- 
itant of shallow water, mostly even of the tidal zone, and its spec¬ 
ies are generally found in great, crowded assemblies, a cross fert¬ 
ilization thus being secured without males. The same seems to hold 
good in Lithotrya, although the specimens of this genus, owing to 
their more hidden living places, have not been observed in such 
great numbers as Mitella . The biology of Scalpellopsis is unknown; 
nevertheless the only species known was found in great numbers 
on a hydroid colony, and thus seems to live in communities. — 
The facts here given show that all the genera hitherto spoken 
of are connected by narrow affinities; on the other hånd, they are 
separated by a rather pronounced gap from the other pedunculated 
cirripeds in their skeleton as well as in their finer characters, and 
in the occurrence of a male. They naturally form a family. Com- 
mon to all of these genera is the skeleton of the peduncle; more- 
