85 
Scuta, i. e. a form with the five „primordial valves“ in accordance 
with Darwins nomenclature. We are moreover justified in sup- 
posing that the skeleton of the ancestors was chitinous, and that 
the calcification in its present shape is a later acquisition. 
From this primitive form the pedunculated Cirripeds seem to 
have developed after two lines. One of these lines leads to the 
extinct genera Archaeolepas and Loricula, and to the recent genera 
Milella (possibly the starting point of the sessile acorn-shells) and 
Scalpellum. The other line has given rise to the other genera of 
stalked Cirripeds, which have kept only the five primordial valves, 
or even reduced their number; in the last case further investig- 
ations will have to tell us, whether all the primordial valves are 
also here indicated in the pupa. 
Kristiania 10- 8—1920. 
