394 BALANIUiE. 



sheath and inner lamina of the parietes in C. testudinaria, taken to- 

 gether, fully equal one third of the entire thickness of the walls. 

 Flattened cavities or tubes run up between the parietal septa for about 

 two thirds of the height of the inside of the shell. With respect to 

 the radii, I have only to add, that the thickness of the inner portion 

 relatively to the generally notched outer lamina, varies considerably. 



Opercular Valves (fig. 1 b — 1 d). — These closely resemble each other 

 in all three species, and have been almost sufficiently described under 

 the genus. The scutum has its occludent margin always sinuous, but 

 to a variable degree. In one specimen there was a deep little pit at the 

 rostral end for the rostral depressor muscle. The terga vary consider- 

 ably in shape, according as the basi-carinal corner is more or less 

 truncated. The external furrow, marking the position of the rudi- 

 mentary spur, varies much in distinctness, chiefly depending upon its 

 nearness to the carinal margin of the valve. 



Mouth and Cirri. — The labrum sometimes has its teeth worn away. 

 The second pair of cirri, relatively to the others, is shorter and thicker 

 than in the two following species. 



2. Chelonobia caretta. PL 14, fig. 2. 



Lepas caretta. Spengler. Skrifter, Naturhist. Selbskabet, 13d. 1, 



1790, Tab. G, fig. 4. 

 Balanus chelytrypetes. Hincks (!) sine descript., Annals of Nat. 



Hist., vol. 5, p. 333. 

 Coronula sulcata. C/ie/iu, Illust. Conch., Tab. 1, fig, 1. 



Shell globulo-co?ivex, extremely massive and heavy ; upper 

 pari worn, sub-striated : radii either not developed or very 

 narrow : parietes without cavities extending up behveen the 

 interrupted, radiating septa. 



Hab. — West coast of Africa ; northern Australia; common. Attached to, and 

 generally imbedded in, the carapaces of turtles. 



General Appearance. — Shell extremely strong, massive, heavy, 

 broadly oval, globulo-convex, though sometimes depressed ; dirty 

 white : surface in the upper part always worn and disintegrated, 

 hence finely striated ; in the lower part a little rugged, slightly folded, 

 and occasionally, in deeply imbedded specimens, much folded or 

 ribbed. Orifice oval, not at all angular, rather exceeding in length 

 one third of the basal diameter of the shell. Radii either not at all 

 developed, or very narrow ; but even in the former case the six lines of 

 suture are plain ; and in the latter case the radii lie at some depth be- 

 neath the surface of the shell. It is remarkable that the compartments 

 are hardly ever arranged symmetrically, the rostrum and carina not 



