CI) THE VOYAGE OF H.M.S. CHALLENGER. 



(1869-70) states the number of recent species is seven, one species (Scalpellwri stroemii) 



having I n described in 1858 by M. Sars. To this number four species were added by 



Prof. G. 0. Sars (1877 and 1880), and one by Prof. Wyville Thomson {Scalpellum 

 regium), from specimens collected during the cruise of the Challenger. The total number 

 of recent species hitherto known, therefore, amounts to twelve. Though' all the records 

 of zoological literature have been carefully searched, I do not feel sure that this number 

 really represents the total of at present known recent species; especially since it 

 appears from the collections made during the cruise of the Challenger that the number 

 of existing species greatly exceeds the above named number. More than forty species 

 will later on be described as new to science ! Yet I need hardly repeat here that it is 

 often an utter impossibility to avoid describing a species as new, the description of 

 which has been published perhaps long ago in the Transactions of some Asiatic or 

 Australian Society, the existence of which has not even come to the knowledge of the 

 recorders of zoological literature. 



The majority of the new species are inhabitants of deep-water. Scalpellum seems to 

 be the only genus of Cirripedia which is often met with in the great depths of the ocean. 

 This strikingly coincides with the common occurrence of this genus in the fossd deposits, 

 especially in secondary strata (Cretaceous period). However, the genus Pollicipes is there 

 to show that we must not attach too much value to this coincidence (see p. 26). Pollicipes 

 is the oldest known fossil genus, all its species live exactly under the same circumstances 

 as the species of Scalpellum, viz., attached to various objects which are found on the 

 bottom, but not a single species has been hitherto taken from any considerable depth ! 



The same observation which Darwin made with regard to the number of specimens of 

 ( lirripeds during the Cretaceous period may be made for the living species of this genus ; 

 although, Darwin says, the number of species was considerable, the individuals were 

 mostly rare. Now the number of species of the genus Scalpellum represented in the 

 Challenger collections amounts to forty-three, and of these twenty-six are represented by 

 a single specimen only, four are represented by two, five by three, two by four, and six 

 only by more than four specimens. 



The great number of species in this genus suggested the idea of dividing it into 

 smaller genera. After careful examination this idea, however, has been given up, as all 

 the species in essential characters correspond as closely, even more closely, with one another 

 than in any other genus of Cirripedia. Nor has it been an easy matter to arrange the 

 species in a natural way, especially because I was not at liberty to make preparations of 

 the parts of the mouth and of the cirri of those species which are represented by single 

 or by two specimens only. For this reason, as well as for the sake of practical utility, I 

 have made use of externally visible characters only, such as are furnished by the con- 

 dition, number, and shape of the different valves of the capitulum, in order to differentiate 

 the various species in the table which follows. 



