Professox' MacGillivray oh the Cirripedia, 177 



different bases, and often coherent, one growing on the peduncle of 

 the other. On both species Cineras membranacea grew very abun- 

 dantly, generally on the peduncles, sometimes on the membrane of 

 the tegmen, seldom on the shell. Otion generally grew indepen- 

 dently, but sometimes individuals adhered to each other ; and very 

 frequently Cineras adhered to the bases of their peduncles, and to 

 their tegmens. 



It does not appear that any corrosive, or otherwise poisonous, 

 substance could be of much avail in preventing their growth, as they 

 do not imbibe nourishment by the base, which is callous. A granu- 

 lar powdery surface, as that of oxidating copper or zinc, would pre- 

 vent their adhesion in a great measure ; and thus, the repeated 

 application of a coating of oil or tallow, mixed with chalk or pow- 

 dered gypsum, or of some such mixture or substance, adhesive, in- 

 soluble in water, but unstable, would, in all probability, prove a 

 remedy. 



On five of these vessels were comparatively few Balani ; but on a 

 London ship, which I visited on the 16th of February, they wero 

 extremely abundant, covering some of the planks almost continuously. 

 These Balani are the only representatives found of the second order 

 of this class of animals. 



The Cirripedia Sessilxa, often named Acorn shells, as well as 

 Barnacles, have the body contained within a conical or cylindrical 

 testaceous tube, affixed by its basis to some solid substance. To this 

 series belong the genera Balanus, Coronula, and a hvf others, form- 

 ing the family of the Balanina. 



In it the animal is ovate, oblong, or depressed, suspended in a 

 testaceous covering, with the hind part uppermost, but at the upper 

 part having generally four moveable testaceous pieces, which separate 

 anteriorly, as does the mantle, which is prolonged at the other end 

 into the coronary tube or shell ; the branchise in the form of two 

 fimbriated laminae attached to the inner surface of the mantle. 



Balanus. Acoen-Shell. 



Animal oblong, somewhat compressed, convex on the baci, incurvate, 

 prolonged anteriorly, with the mouth prominent, and furnished with a 

 pair of external, adnate, pointed, incurvate palpi, and three pairs of 

 maxillary appendages, of which the thin terminal lamina is ciliated with 

 spines or bristles ; the body narrowed behind, with twelve pairs of pedi- 

 cellate, tapering incurvate, multiarticulate, lobulate, ciliate cirri; the 

 ovarian tube very long, tapering, annulate ; the branchiae lateral, at the 

 fore part of the body, each composed of an oblong generally fibriated 

 mass. 



Tegmen compressed or pjTamidal above, with four triangular, taper- 

 ing, pointed plates, forming two lateral valves separating in the median 

 line, and mobile; its dermal lining affixed below to the interior of the 

 coronary tube, which it lines in its whole extent beaeath, and is closed 

 at the base. 



VOL. XXXIX. NO. LXXVII.— JULY 1845. U 



