PREFACE. XI 



been permitted to examine a considerable number of au- 

 thentically named specimens, (to which I have attached the 

 sign (!) used by botanists,) so that several of my synonyms 

 are certainly correct. 



The Lepadidae, or pedunculated Cirripedes, have been 

 neglected under a systematic point of view, to a degree 

 which I cannot quite understand : no doubt they are 

 subject to considerable variation, and as long as the 

 internal surfaces of the valves and all the organs of the 

 animal's body, are passed over as unimportant, there 

 will occasionally be some difficulty in the identification 

 of the several forms, and still more in settling the 

 limits of the variability of the species. But I suspect 

 the pedunculated Cirripedes have, in fact, been neglected, 

 owing to their close affinity, and the consequent neces- 

 sity of their being included in the same Work with the 

 Sessile Cirripedes; for these latter will ever present, 

 I am fully convinced, insuperable difficulties in their 

 identification by external characters alone. 



I will here only further remark, that in the Introduction 

 I have given my reasons for assigning distinct names to 

 the several Valves, and to some parts of the included 

 animal's body ; and that in the Introductory Remarks, 

 under the general description of the Lepadidae, I have 

 given an abstract of my Anatomical Observations. 



