38 FOSSIL CIRRTPEDIA. 



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, i. 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 radii 

 been specially thickened by numerous sinuous denticulated plates, springing from the inner 

 lamina 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 alse, also, are very unusually thick : but, notwith- 

 standing their thickness and the thickness of the compound radii, owing to the depth oi 

 the folds of wall, they are separated from each other by a considerable space, and the alas, 

 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 alas rest, and the compound radii, there are 

 in two of the three recent species, open chambers, six in number, occupied by the ovarian 

 caeca ; but in the fossil C. barbara 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. 



Coronula Barbara. Tab. II, fig. 8a — 8e. 



Coronulites diadema (?) Parkinson. Organic Remains (1811), vol. iii, p. 240, 



pi. 16, fig. 19. 



C. testa (probabiliter) coroni/ormi, costis longitudinalibus convexis, aciebus earum cre- 

 natis, superficie interna et externa cristis transversis asp era ; radiis modice crassis ; spatic 

 inter radios et alas solide impleto. 



Shell (probably) crown-shaped, with longitudinal convex ribs, having their edges 

 creuated, and their surfaces rugged, both externally and internally, with transverse ridges : 

 radii moderately thick ; the space between the radii and the alas solidly filled up. 



Fossil in Red Crag, (Bawdsey and Sutton) ; Mus. S. Wood and Geological Society. 



