269 
phosis into the typical Lepas now takes place. The primordial 
plates are developed, and exhibit a peculiar shape, very different 
from that of the capitulum plates of the outgrown Lepas. The 
carina is boat-shaped, and long; tergum is quadrangular with a 
short occludent margin, a long, feebly concave scutal margin, and 
strongly excavated carinal and free dorsal margins of almost equal 
lengths. The scuta are triangular with almost straight occludent 
margin, convex tergo-carinal margin, and concave basal margin, so 
that the posterior basal angle is 
rather pointed. 
Generally also the incipient 
calcification can be observed in 
the small cirriped within the 
pupa cover. The cover then splits 
along the dorsal line, commenc- 
ing at its upper (posterior) end; 
the small Lepas now extends its 
peduncle till it attains almost 
the same length as the capitulum. 
The pupa cover yet often for a 
while adheres to the peduncle, 
to be thrown off when the calci¬ 
fication of the capitulum plates 
is more obvious, and the form¬ 
ation of growth lines has com- 
menced. 
During growth the peduncle and the capitulum add to their 
dimensions after a proportionate scale. The calcification of the plates 
gives evidence that in Lepas, in contradistinction to Scalpellum, 
and Pollicipes, the greater capacity of lime secretion is localized 
to the central areas of the capitulum sides, and the umbones of 
the plates, as indicated by the primordial valves, are situated cor- 
respondingly, the umbo of the terga apically, that of the carina, 
and scuta basally (Fig. 28). — 
In the material of young stages from the os sepium the forma 
squamosa Fischer with its spiny plates prevails; some of the 
specimens apparently little by little lose their spiny appearance. 
Among the still more numerous specimens of the Janthina shells 
a b 
Fig. 28. Lepas pectinata from 3(5° 00’ S., 
150° 20 ’ E. a specimen with primordial 
valves developed, left half of the pupa 
cover partly llared off; b young spec¬ 
imen with primordial valves yet pre- 
served on the umbones of the calcified 
plates. [a X 25, b X 12 .b]. 
