132 THE FAUNA OF THE DEEP SEA 



barnacles and acorn shells, Dr. Hoek writes in the 

 ' Challenger ' monograph : — 



' Though unquestionably by far the greater part 

 of the known Cirripedia are shallow-water species, 

 and though some of the species are capable of living 

 at a considerable variety of depths, as, for instance, 

 Scalpellum stroemii, yet it must be granted that the 

 number of true deep-sea species of Cirripedia is very 

 considerable.' Only two genera, however, occur in 

 depths of over 1,000 fathoms, and these — Scaljpellum 

 and Verruca — occur also as fossils in secondary and 

 tertiary deposits. The oldest of all fossil cirripedes, 

 however, namely, Pollicipes, never occurs, at the 

 present day, in deep water, but is purely littoral or 

 neritic in habit. But what is perhaps more interest- 

 ing still is the fact, that, when we come to compare 

 the living and the fossil species, we find that in the 

 one genus (Scaljpellum) the deep-sea forms have pre- 

 served the more archaic characters, and in the other 

 (Pollicifes) the shallow-water forms. 



Here then we are presented with a veritable 

 puzzle for which we can at present frame no manner 

 of answer. Pollicipes on the one hand — like Lingula 

 among the brachiopods — has been able to maintain 

 itself almost unchanged amid the tremendous struggle 



