178 Professor MacGillivray on the Qirrivedia. 



Coronary tube, or shell, conical, truncate, of six u;3ited pieces, pre- 

 senting externally six triangular elevated areas, broader belovr, and sis 

 narrower depressed areas, broader above ; the anterior elevated area 

 largest, the anterior lateral and the dorsal next in size, the posterior 

 lateral very small ; the base formed by a calcareous plate, or sometimes 

 membranous ; the aperture ovate, triangular, or pentagonal. In the 

 upper part of the coronary tube internally, an accessory calcareous tube 

 composed of six iuibricated thin plates. 



The species of this genus are very numerous, and, for the most 

 part, vei-y ill described. Some are to be found in evei-y part of the 

 maritime world, adhering to rocks, stones, wood, shells, and other 

 objects. One only has occurred on the Ichaboo vessels. 



1. Balanus porcatus. 



Shell conical, strong, obliquelj' truncate, with the aperture rather 

 small, subovate ; the elevated areas with prominent, straight, compressed, 

 obtuse, white ridges, separated by flattened faintly striate depressions, 

 covered with a reddish epidermis ; the depressed areas narrow, flat, 

 shining, finely striulate ; the accessory tube transversely distantly lamel- 

 loso-striate ; the opercular plates transversely rugoso-sulcate, the an- 

 terior acute, the posterior with the apex acuminate and incurvate, the 

 base with a narrow process, from which a groove runs to the apex. 



Animal ovate, somewhat compressed, with the anterior part of the 

 body very convex on the back, and prolonged antoriorlj', where it is 

 attached by two strong muscles to the coronary tube, and by muscular 

 fibres to the lower part of the mantle, and covered with a thin mem- 

 branous integument, becoming firmer on the lined part, which is short 

 and rather broad. The mouth prominent, with a vaulted, bullate, 

 rounded lip, having externally a pair of adnate, pointed, ciliate palpi, 

 and three pairs of maxillary appendages ; the first pair denticulate at 

 the end, the second broad and ciliate, the third more pointed and ciliate. 



The first pair of feet very small, and quite close to the mouth ; on 

 each side of the hind part of the body five feet, each compressed, 

 obliquely grooved on the back, and bearing a pair of long, compressed, 

 tapering, incurvate cirri, articulated, lobulated on the inner edge, and 

 there ciliate with divergent rows of bristles, generally two or three 

 bristles on each side of each lobule ; the last cirri with thirty-five joints. 



At the fore-part of the body, and connected with the mantle, on each 

 side, is a large oblong branchial body. 



The narrow part of the body, to which the abdominal feet are at- 

 tached, is rather bi'oad, convex above and beneath, in the latter aspect 

 faintly grooved across. It ends in a very long, slender, tapering, an- 

 nulated tube, curved inward-;, but, when extended, much longer than the 

 cirri. At the base of this tube, between the last two feet, is the anus, in 

 the form of an oblong aperture, without operculum. 



The general colour of the body is yellovvish-whito, posteriorly light 

 roddish-brown : the feet pink, the cirri pale j-cllowish-gre}'. 



The mantle is very thin, and lines the calcareous plates of the oper- 

 culum, as well as the epidermis at their base, beyond which it extends, 

 becoming much thicker all round, down to the base of the coronary 

 tube, extending over the basal plate. Within it, the proper envelope of 

 the body is continuous with muscular fibres affixed to the base of the 

 tuube. 



The tegmen is of a pyramidal form, membranous below, where it is 

 attached to the base of the accessory calcareous tube, above with the 



