PREFACE. IX 



would be superfluous here to repeat the same list of 

 authors. I will only add, that since the date, 1834, of 

 the above works, the only important papers with which 

 I am acquainted, are, 1st. Dr. Coldstream ' On the 

 Structure of the Shell in Sessile Cirripedes,' in the 

 ' Enclycopsedia of Anatomy and Physiology;' 2d. Dr. 

 Loven ' On the Alepas squalicola,' (' Ofversigt of Kongl. 

 Vetens.,' &c. Stockholm, 1844, p. 192,) giving a short 

 but excellent account of this abnormal Cirripede; 3d. 

 Professor Leidy's very interesting discovery, (' Proceed- 

 ings of the Academy of Natural Sciences/ Philadelphia, 

 vol. iv, No. I, Jan. 1848,) of eyes in a mature Balanus; 

 4th. Mr. A. Hancock's Memoir, (' Annals of Natural 

 History, 2d series, Nov. 1849,) on his Alcippe lampas, 

 the type of a new order of Cirripedes ; 5th. Mr. Goodsir's 

 Paper, ('Edinburgh New Philosoph. Journal,' July 1843,) 

 on the Larvae in the First Stage of Development in 

 Balanus; 6th. Mr. C. Spence Bate's valuable Paper on 

 the same subject, lately published, (Oct. 1851,) in the 

 ' Annals of Natural History;' and lastly, M. Bernhardt 

 has described, in the ' Copenhagen Journal of Natural 

 History, Jan. 1851,' the Litliotrya Nicobarica, and has 

 discussed its powers of burrowing into rocks. 



I have given the specific or diagnostic characters, de- 

 duced from the external parts alone, in both Latin and 

 English. As I found, during the progress of this work, 

 that a similarly abbreviated character of the softer internal 

 parts, was very useful in discriminating the species, I 

 have inserted it after the ordinary specific character. 



In those cases in which a genus includes only a single 



