306 Mr. A. Hancock on a Burrowing Barnacle 



ther with Cliona, destroys the shells of the larger mollusks of 

 our coast. Cliona enters by the outer surface of the living shell, 

 and rapidly spreads over the whorls ; but it is not until after 

 death that the inner surface becomes much affected by it. Then 

 this Cirripede commences its ravages on the columella, which it 

 soon deprives of more than half its substance, and afterwards so 

 reduces it and the inner surface of the whorls, that this once 

 secure retreat of the moUusk, losing all power to resist external 

 forces, speedily becomes a crumbling ruin. 



Little is to be seen externally, — a small slit in the shell or 

 matrix marks the position of the head (PL VIII. figs. 1 & 2 6). 

 This slit, which is one-eighth of an inch long, is rounded and 

 gradually enlarged towards one end, and tapers to a tolerably 

 fine point at the other, which is generally a little bent. At this 

 extremity the shell is mostly stained of a reddish hue (PI. VUI. 

 figs. 1 & 2 a) — the stain being well-defined and of an ovate or 

 fan-like form, increasing in size for about -3%^^^ ^^ ^^ inch back- 

 wards, and having a few pale radiating lines, which converge 

 towards the slit ; on these lines there are a few minute punctures 

 irregularly distributed ; but whether for functional purposes, or 

 merely accidentally resulting from the close approximation of 

 the animal to the surface, could not be determined : they are not 

 unfrequently partially closed up with calcareous matter. 



The stain is caused by the animal appearing through, which 

 lies immediately below the surface of the matrix. This must be 

 broken before the animal (PL VIII. figs. 3, 4, 5) can be removed, 

 and then it is found to be y*2 ths of an inch long, and y%ths of an 

 inch wide at the broadest part, of an irregular ovate form consi- 

 derably depressed behind, b, where it expands into a broad circular 

 disc ; and narrow and compressed in front, a, forming a sort of 

 produced neck or head with a longitudinal slit, d, on the upper 

 surface; — the general form resembling considerably a Roman 

 lamp, the slit representing the orifice for the passage of the wick. 

 The produced portion or head corresponds to the valvular part of 

 the pedunculate Cirripede, and contains the body and arms or 

 feet, — the slit being analogous to the usual opening for the pas- 

 sage of these prehensile organs : there are, however, no shelly 

 plates whatever, the mantle being soft, fleshy and highly con- 

 tractile, having the surface distinctly marked with fine longitu- 

 dinal muscular fibres below; this part arches deeply into the 

 matrix, and joins rather abruptly the under surface of the de- 

 pressed disc-like portion of the animal considerably behind the 

 posterior end of the longitudinal slit. The margins of this slit 

 are perfectly straight, thickened, and have somewhat the appear- 

 ance of horn, but cannot be considered as forming distinct plates, 

 though they compose, as it were, two valvular lips (figs. 3 & 5 c). 



