xiv PROOFS, ILLUSTRATIONS, AUTHORITIES, ETC. 



by the animal subsequently to its emersion from the egg. In the 

 first it is possessed of no hard covering, has two long antennae and 

 three pairs of arms tipped with bristles, by which it freely moves 

 through the water; and it is believed to be furnished with eyes. 

 At a subsequent time the animal fixes itself by its antennse, and the 

 shell, of leathery consistence, begins to be formed in one piece at the 

 back of the body ; and at this period the eyes are very distinct and 

 brilliant. In the third stage, the divisions of the shell begin to 

 appear, and it more completely encloses the animal, at the same time 

 becoming more solid by the deposition of calcareous matter. Soon 

 after the animal completely fixes itself, the old integuments, together 

 with the antennse and eyes, are thrown off. The fourth stage is that 

 in which the development is completed." Carpenter : Comparative 

 Physiology, 1839. 



The Cirrhopoda are in two divisions. " One division, the Balani 

 (acorn-shells) have the bases of their pyramidal shells fixed upon 

 rocks or other large masses of matter ; whilst the Lepades (barnacles) 

 attach themselves to floating bodies by a membranous tube, some- 

 times of considerable length. "--Carpenter. That the latter or 

 pedunculated cirrhopods are the inferior family may be speculatively 

 inferred from the fact of their fixing power being of a less determined 

 character than that of the other, the sessile habit being apparently 

 the perfection of this line of being. That the Balani display an 

 affinity to the decapod Crustacea, and the Lepades to the Entomos- 

 traca, is an opinion of Mr. J. Y. Thomson of Cork, who has distin- 

 guished himself by his researches in the development of the Cir- 

 rhopoda. 



Now, such being the elevated position of the Cirrhopoda as an 

 order, and such being at least speculatively the comparative charac- 

 ter of its two great divisions, it is very remarkable to find no fossil 

 cirrhopoda before the oolite formation, and that though pedunculated 

 cirrhopods begin then, and make a large appearance in the chalk, 

 none of the sessile family are presented till the tertiary. 



" The oldest known pedunculated cirripede is a Pollicipes, dis- 

 covered by Professor Buckman in the Stonesfield slate, in the Lower 

 Oolite. . . . . I have not as yet heard of any cirripede having been 

 as yet discovered in the Upper Oolite, or in the Wealden formation. 

 During the deposition of the great Cretaceous System, the Lepadida? 

 arrived at their culminant point; there were then three genera, and 

 at least thirty-two species, some occurring in every stage of this 



system I believe that very many more will yet be discovered. 



" No true Sessile Cirripede has hitherto been found in any 

 Secondary formation : considering that at the present time many 

 species are attached to oceanic floating objects, that many others live in 

 deep water in congregated masses, that their shells are not subject to 

 decay, and that they are not likely to be overlooked when fossilized, 

 this seems one of the cases in which negative evidence is of consider- 

 able value Sessile cirripedes are first found in Eocene de- 

 posits, and subsequently, often in abundance, in the later Tertiary 



