4 INTRODUCTION. 



The Tergum has been called the " dorsal/ 5 the "pos- 

 terior/' the " superior/ 5 the " central/ 5 the " terminal/ 5 

 the " postero-lateral/ 5 and the " latero-superior" valve. 

 The Carina has received the first two of these identical 

 epithets, viz. the " dorsal" and the " posterior ;" and 

 likewise has been called the "keel-valve." The con- 

 fusion, however, becomes far worse, when any individual 

 valve is desciibed, for the very same margin which is 

 anterior or inferior in the eyes of one author, is the 

 posterior or superior in those of another; it has often 

 happened to me that I have been quite unable even to 

 conjecture to which margin or part of a valve an author 

 was referring. Moreover, the length of these double 

 titles is inconvenient. Hence, as I have to describe all 

 the recent and fossil species, I trust I may be thought 

 justified in giving short names to each of the more im- 

 portant valves, these being common to the pedunculated 

 and sessile Cirripedes. 



The part supported by the peduncle, and which is 

 generally, though not always, protected by valves, I have 

 designated the Capitulum. 



The title of Peduncle, which is either naked or squa- 

 miferous, requires no explanation ; the scales on it, and 

 the lower valves of the capitulum, are arranged in whorls, 

 which, in the Latin specific descriptions, I have called by 

 the botanical term of verticillus. 



I have applied the term Scutum to the most important 

 and persistent of the valves, and which can generally be 

 recognised by the hollow giving attachment to the 

 adductor scutorum muscle, from the resemblance which 

 the two valves taken together bear to a shield, and from 

 their office of protecting the front side of the body. 

 From the protection afforded by the two Terga to the 

 dorso-lateral surface of the animal, these valves have 

 been thus called. The term Carina* is a mere trans- 



* In the Carina of Eossil Species of Scalpellum, I have found it necessary 

 to distinguish different parts, viz., A, the tectum, of which half is seen ; 

 B, the parietes ; and C, the intra-parietes. 



