PREFACE. 



My duty, in acknowledging the great obligations 

 under which I lie to many naturalists, affords me most 

 sincere pleasure. I had originally intended to have 

 described only a single abnormal Cirripede, from the 

 shores of South America, and was led, for the sake of 

 comparison, to examine the internal parts of as many 

 genera as I could procure. Under these circumstances, 

 Mr. J. E. Gray, in the most disinterested manner, sug- 

 gested to me making a Monograph on the entire class, 

 although he himself had already collected materials for 

 this same object. Furthermore, Mr. Gray most kindly 

 gave me his strong support, when I applied to the 

 Trustees of the British Museum for the use of the public 

 collection ; and I here most respectfully beg to offer my 

 grateful acknowledgments to the Trustees, for their most 

 liberal and unfettered permission of examining, and when 

 necessary, disarticulating the specimens in the magnificent 

 collection of Cirripedes, commenced by Dr. Leach, and 

 steadily added to, during many years, by Mr. Gray. 

 Considering the difficulty in determining the species in 

 this class, had it not been for this most liberal permission 

 by the Trustees, the public collection would have been of 



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