35 FOSSIL CIRRIPEDTA. 
cavity, open at the bottom of the shell, and running up to the apex : these cavities are quite 
external to the cirripede, and are occupied by the epidermis of the whale to which the 
Coronula is attached : homologically they are only deep longitudinal furrows, and they would 
still have been furrows, had not the transversely elongated ends of the folds, 7. e., the 
circumferential loops, in all cases, after early growth, grown into close contact. The ends of 
these loops are generally locked together by rows of minute teeth. In all the species, 
when young, the wall of each compartment is folded three times, and therefore the whole 
shell has eighteen folds. 
The radii, normally, are only part of the wall, modified by growing against an opposed 
compartment; and hence the radius in Coronula would have been extremely thin, like the 
wall, and the sutures between the six compartments excessively weak, had not the radu 
been specially thickened by numerous sinuous denticulated plates, springing from the inner 
Jamina of the true radius, and running downwards, attached to the folded wall of the com- 
partment to which the radius belongs, and with their free edges pressed against the folded 
wall of the opposed compartment. Hence the radii may be said to be compound. For 
the sake of strengthening the sutures, the alee, also, are very unusually thick: but, notwith- 
standing their thickness and the thickness of the compound radii, owing to the depth of 
the folds of wall, they are separated from each other by a considerable space, and the ale, 
instead of resting in chief part, as they should do, on the inner lamina of the radius, have 
to rest on special plates, developed apparently from the sheath. In the upper part of the 
shell, between the special plates on which the ale rest, and the compound radii, there are 
in two of the three recent species, open chambers, six in number, occupied by the ovarian 
ceca; but in the fossil C. darbara these chambers are almost filled up solidly by shell. I 
hope that the terms used in the following description may be now in some partial degree 
rendered intelligible. 
ConoNuLA BARBARA. ‘Tab. II, fig. 8a—8e. 
(oe) 
CoRONULITES DIADEMA (?) Parkinson. Organic Remains (1811), vol. iii, p. 240, 
pl. 16, fig. 19. 
C. testd (probabiliter) coroniformi, costis longitudinalibus convexis, aciebus earum cre- 
natis, superficie internd et externd cristis transversis asperd ; radiis modicé crassis ; spatio 
inter radios et alas solide impleto. 
Shell (probably) crown-shaped, with longitudinal convex ribs, having their edges 
crenated, and their surfaces rugged, both externally and internally, with transverse ridges : 
radii moderately thick ; the space between the radii and the alz solidly filled up. 
Fossil in Red Crag, (Bawdsey and Sutton) ; Mus. S. Wood and Geological Society. 

