172 Professor MacGillivray on the Cirripedia, 



very convex on the back, moderately narrowed behind ; anteriorly soft 

 and prolonged into the peduncle, with a very thin membranous integu- 

 ment, which becomes firmer on the hind part ; the mouth prominent, with 

 a vaulted, bullate, rounded lip, having externally two thick, adnate palpi, 

 free at the end, curved forwards and inwards, with a long incurved si^i- 

 nose tip, and three pairs of incurvate, compressed, maxillar appendages, 

 lamelliform at the end. The first or outer pair, with the terminal lamina 

 Eubtriangular, pointed, with six external marginal, acuminate teeth, of 

 which the posterior is very large, and the anterior very minute ; the 

 second with the lamina subtriangular, with five short, convex, ciliated 

 lobes ; the third or inner narrower and ciliate. 



The first pair of feet, shorter than the rest, are placed immediately 

 behind the mouth ; the second pair at some distance ; the rest close to- 

 gether. The first pair subcylindrical, compressed, obliquely and deeply 

 grooved on the back, with four joints ; their cirri short, broad, tapering, 

 with seven joints ; the other feet compressed, obliquely grooved, with 

 two joints, and longer, compressed, tapering cirri, the last having seven- 

 teen joints ; all the cirri lobed and ciliate on the edge next the mouth ; 

 the bristles general!}' ten or twelve on each lobe, in two series, the dor- 

 sal bristles very small and adpressed. 



At the base of the first foot externally are two long, tapering, bran- 

 chial filaments ; and there is a very small knob at the base of each of the 

 other feet except the last. 



The narrowed part of the body, to which the five pairs of abdominal 

 feet are laterally attached, is narrow, smooth, and horny above, trans- 

 versely grooved or subarticulate beneath. It ends in a very long, slen- 

 der, tapering tube, usually curved inwards, but, when extended, much 

 exceeding the last cirri in length. At the base of this tube, on the dor- 

 sal aspect, is the anus, over which are two oblong, mobile, horny 

 plates. 



The general colour of the body Is a dingy-grey or whitish, posteriorly 

 darker, the legs and cirri dusky-brown. 



There is a transverse muscle attached to the body behind, and on 

 either side to the tegmen ; the ovary passes from a third to half way 

 down the pedicle, which is not contracted above, but gradually tapers 

 downwards. 



The mantle is very thin, generallj' of a pale greyish-blue, as is its con- 

 tinuation into the peduncle, but having on each side three longitudinal 

 bands of dusky pigment ; these colours distinctly appearing through the 

 epidermis, which is 3-ellowish-grey or brownish, and transparent. 



The tegmen subovate, subtetragonal, being obliquely truncate above, 

 moderately compressed, sustained, as it were, by the fiive very slender 

 calcareous pieces. 



The anterior pair nearly straight, linear, very thin, with an oblique 

 oblong process from above the middle, directed upwards and backwards ; 

 the upper pieces marginal, linear, slightly recurved, a little divergent 

 anteriorly, generally more divergent behind ; the dorsal piece linear, 

 curved convexly below, concavely above, and meeting the upper pieces 

 at the posterior angle. 



The peduncle about the length of the tegmen ; its internal laj^er often 

 coloured pale-blue, with or without a continuation of the dusky bands 

 of the tegmen, sometimes light-brown, or pale yellowish-grey. 



Verj' young individuals have the epidermis extremelj' thin, transpa- 

 rent, the calcareous pieces spicular, the colours paler, generally without 

 the blue tinge. 



The general form does not vary nmch ; but that of the calcareous 

 pieces is subject to great variation in form, curvature, and thickness. 



