4 THE VOYAGE OF H.M.S. CHALLENGER. 



to one and the same division of the genus. I have been able to study the male of one 

 of these (Scalpellum regiurn [Wyv. Thorns.], Hoek) more in detail; in all essential 

 respects the males of the other twelve agree with it. 



The twenty-four species of Scalpellum, the males of which arc known at present, may 

 be classified with regard to the structure of these males in the following way : — 



A. Species, the males of which show a distinct capitulum and peduncle : — 



Scalpellum peronii, Gray, sp. Scalpellum rostratum, Darwin. 



Scalpellum villosum, Leach, sp. 



All these are shallow water species. 



B. Species, the males of which do not show a division of the body into a capitulum 



and a peduncle, but yet are furnished with rudimentary valves : — 



Scalpellum vulgarc, Leach. 

 rutilum, Darwin. 

 ornatum, Gray, sp. 

 intermedium, Hoek. 



Scalpellum parallelogramma, Hoek. 

 elongatum, Hoek. 

 tritonis, Hoek. 

 triangulare, Hoek. 



Species occurring in depths varying between shallow water and 700 fathoms. 



Species, the males of which do not show a division of the body into a capitulum 

 and a peduncle, and arc not furnished with rudimentary valves : — 



Scalpellum marginatum, Hoek. 

 str6mii, Sai\s. 

 compressum, Hoek. 

 iiiimphocola, Hoek. 

 velutiitum, Hock. 

 cximium, Hoek. 



Scalpellum gigas, Hoek. 



regium (Wyv. Thorns.), Hoek. 



darwinii, Hoek. 

 tenue, Hoek. 

 dubium, Hoek. 

 jlnvum, Hoek. 



Scalpellum pedunexdatum, Hoek. 



With the exception of three (Scalpellum pcduueulatum, Sc<dpellum stroma, and 

 Scalpellum nymphocola), these species occur in depths of upwards of 1000 fathoms. 

 The depths at which Scalpellum stromii and Scalpellum nymphocola were collected are 

 less considerable; these species, however, belong to the arctic fauna, which, as is well 

 known, shows numerous instances of deep-sea animals occurring in rather shallow water. 

 Scalpellum pedunculatum was taken from a depth of 150 fathoms only. 



