970 ON CRUSTACEANS OF THE GENUS SERGESTES. [Dee. 1, 
common at the surface, but Ortmann communicates that it has 
been captured in the intermediate net from 700-500 m.; and if 
some of the specimens recorded by Bate (p. 390) as 38, 48, and 50 
mm. long, and coming respectively from 600, 2150, and 445 fathoms, 
really belong to this species, it grows considerably larger in the 
deep sea, as no specimen from the surface exceeds 30 mm. Finally, 
S. cornutus, Kr., and S. edwardsi, Kr., are the only instances of 
the 14 species which only have been captured at the surface (and 
in vertical nets drawn up from 500 m. to the surface). In this 
paper I have described the mature forms of S. vigilax, Stimps., 
H. J. H., S. penerinki, Bate, H. J. H., and S. incertus, n. sp., 
which have all been captured at the surface. S. tenuiremis, Kr., 
H. J. H., and S. corniculum, Kr., H. J. H., are common at the 
surface in the Mastigopus-stages; above I have described the 
younger black-eyed forms of both species, also captured at the 
surface, but the adult stages are quite unknown and must, in 
my opinion, be true deep-sea forms. Of S. diapontius, Bate, and 
S. mediterraneus, m., only the Mastigopus-forms are known, and 
the adults are certainly inhabitants of the depths. (S. profundus, 
Bate, from 1375 and 2550 fathoms, I omit, as the species is too 
uncertain, ) 
Though we still know too little of the bathymetrical distribution, 
it must, I think, be taken as proved that at least two-thirds of the 
species inhabit the depths of the sea when the animals have quite 
arrived at maturity (or at least at their full length, cfr. S. atlanticus). 
I can say that with two exceptions—my single adult specimen of 
S. incertus, m., and Kroyer’s specimen of S. arcticus, Kr.,—no 
specimen exceeding 30 mm. in length recorded in the existing 
literature or seen by me has been captured near the surface, but all 
large specimens, from 30 mm. to 113 mm. (S. inous, Fax.) in length, 
have been secured with trawl or dredge coming from a considerable 
to a very great depth (345-2574 fath.). Faxon writes on p. 249: 
“There can be no doubt that the deep-sea Crustacea occasionally 
come to, or very near to, the surface,’ and he communicates 
several instances; I think that, for instance, my single and Jarge 
specimen of S. incertus, m., 47 mm. long, has been secured on such 
a visit. It is evident that the animals as true swimming forms do 
not live on the bottom itself, but, I presume, in the water- 
stratum just above it. 
As will be seen from this paper, our knowledge of this rich and 
eurious genus is still rather imperfect. A good monograph, based 
on the study of the collections in the seven or eight museums which 
possess materials of importance, would be extremely valuable 
and elicit numerous new facts; and future deep-sea expeditions, 
making use of the trawl, intermediate net, vertical net, and surface 
net, would be sure to discover new species and especially enlarge 
our knowledge of the metamorphosis and distribution. 
