INTRODUCTION. 
Crrripepia may be divided, as I have recently shown in a monograph on the Balanide 
published by the Ray Society, into three Orders: of these, the Thoracica includes all 
ordinary Cirripedes, and all ever likely to be found fossil, and therefore the two other orders 
may be here passed over without notice. The Thoracica contains three Families: the 
Balanide or Sessile Cirripedes, which in a recent state so abound on the shores of almost 
every quarter of the world, and which are so frequently found in Tertiary deposits; the 
Verrucide, which includes only a single genus very singular from its asymmetrical 
shell; and the Lepadidze, or Pedunculated Cirripedes ; of the latter, the Fossil species have 
been already published by the Palzontographical Society. The Balanidz and Verrucide will 
be treated of in the followimg pages. As yet only sixteen species in these two families 
have been found fossil in Great Britain ; and of these sixteen, nine are still living forms. 
As the latter are known only imperfectly in their fossil condition, and as they have lately 
been described by mein full detail, I have thought it best here only to make a few remarks 
on such portions of the shells of each species as have hitherto been discovered, adding a 
few illustrations, such as appeared to me desirable. The extinct species will be fully 
described: of these, all the figures given are from British specimens. But of the species 
found both living and fossil, I have in several instances (always so stated) given drawings 
from recent specimens; some of the valves either not having been found fossil, or 
found only in an imperfect and not characteristic condition. As so few species in the 
several genera are known in a fossil condition, I have thought it quite superfluous to give 
long generic descriptions, which would have required constant references to many species 
exclusively found living. 
In my former monograph on the Fossil Lepadide, I remarked how much the natural 
i 
