oe 
Professor MacGillivray on the Cirripedia. 295 
been found, first by Mr Thompson, and subsequently by Burmeister, 
Wagner, and Audouin, to undergo in their earlier stages. In the 
part of Scotland in which I am at present located, the pedunculate 
species, of which only one, Scalpellum vulgare, appears to be truly 
indigenous, are of so rare occurrence, that the recent arrival of the 
multitudes which crowded the uncoppered submersed portions of the 
hulls of some vessels with guano from Ichaboe, could not fail to 
afford great pleasure. These animals, now clearly shewn to belong 
to the great type of the Entomozoa, and to approximate to certain 
Crustacea, have not, I think, been well described by any of the ex- 
cellent naturalists who have written upon them in our country; and 
therefore I have thought, that a full description of those so fortu- 
nately brought under notice may be not without use, if not to the 
present race of compilers, at least to their successors, and to those 
younger zoologists who may not have equal opportunities of observ- 
ing them. 
The six vessels on which the cirripedia to be described were 
found, had been absent from seven to nine months ; in which time 
they had traversed the Atlantic Ocvan, by the Azores and Brazil, 
to near the Cape of Good Hope ; and, after remaining several weeks 
at Ichaboe, a small islet, not far from Cabo Negro, on the west coast 
of Southern Africa, and in lat. 15° 26’ S., had returned by St Helena 
and the Cape Verd Islands. None of the species are peculiar to 
Ichaboe, where, on the contrary, they seemed less healthy than they 
had previously been. They began to be observable at about the end 
of the first fortnight of the voyage out, and became sickly on the 
homeward route, to the north of the Azores. When the vessels 
arrived at Aberdeen, they were all dead, although on two they were 
perfectly fresh and plump. It is probable, however, that in summer 
they would have been alive; and that their death was caused by the 
severe frost which then prevailed, as they were mostly liable to occa- 
sional emersion. 
It may be unnecessary to remind the expert zoologist, but it is pro- 
per to intimate to those readers who have not made this class of ani- 
mals a special study, that the cirripedia, all of which that I have 
examined, agree with each other more closely in their structure than 
the members of any other class of the great type to which they be- 
long, are distinguished by the following characters. 
Their body is soft, enveloped in a membranaceous integument, 
incurved, and placed with the back beneath, and the hind part above. 
It is enclosed in a thin mantle, and a membranous or coriaceous teg- 
men, in which are formed several calcareous plates, varying in the 
different genera, and wanting only in one; subovate at its lower or 
anterior part; very convex on the back; attenuated and subarticu- 
- lated at the upper or posterior end. It has attached to it, on either 
side, six limbs, cach terminated by two long, slender, horny, many- 
jointed cirri. The first pair of these limbs, placed not far from the 
