The large male measures 88 mm. from the tip of the rostrum to the apex of the 

 telson ; though very large, it is considerably smaller than Faxon's type, which was 1 1 3 mm. 

 long. This species is similar and very closely allied to 5. japonicus Bate (S. mollis S. I. Smith) 

 but it is very much larger, and differs, as already pointed out by Faxon and Alcock, sharply 

 by the posterior branchia of third pair of thoracic legs. The specimens from the "Siboga" have 

 the third maxillipeds mutilated, consequently I cannot fill up the gap in our knowledge. 



The petasma (figs. \a — \c) which affords specific characters, has never been described. 



Lamina externa {lam.) of pars externa (e.) is very long, a little longer than processus uncifer (pte.), 



and its proximal half has its outer margin slightly convex. The processus ba'salis (pó.) is rather 



slender, moderately short, with an acute angle on the otherwise moderately broad terminal part. 



The middle portion of pars media (;«.) is rather slender. Processus ventralis (pv.) is long, nearly 



straight, moderately slender, slightly broader beyond the middle than at the base, while its 



distal fifth tapers to the subacute end. Lobus armatus (Ja.) is much curved, decreasing from 



before the middle to the narrowly rounded end; somewhat less than its proximal half of the 



inner side has a moderate number of invaginated hooks, and a somewhat shorter distal portion 



of the anterior and the outer sides has several hooks, while the long middle portion 



of the lobe is completely unarmed. Lobus connectens Je.) is long, protruding beyond 



the other rami of pars media, thick at the base, subconical, with the end narrow but obtuse; 



the outer surface of the lobe has a good number of hooks, the most proximal among them 



quite small, and the terminal narrow part of the lobe has similar small hooks both on the 



inner and the anterior surface. Lobus terminalis (//.) is very short and thick, with a moderate 



number of small hooks at the end and along the distal part of the outer and the inner margin. 



Lobus inermis Ji.) is only about one-third as long as lobus connectens, curved, very slender with 



the end acute and without any hooks. Pars astringens (a.) does not exhibit any peculiarities. 



The petasma described is allied to that of S. japonicus 1 ), but differs in several features; 

 lobus inermis is more slender, curved and acute; lobus connectens has its proximal two-thirds 

 much thicker and besides a lower number of hooks, as the lobe in S. japonicus has numerous 

 hooks on the major part of its posterior surface and at the distal half of the inner margin . 

 lobus armatus is much thicker than in the other form and its long middle portion without 

 hooks, while in S. japonicus the lobe has numerous hooks distributed in its whole length both 

 on the posterior side and especially on its anterior side towards the inner margin. Among these 

 characters those found in the last-named lobe are probably the most valuable. 



Distribution. — The type was secured in the tropical East Pacific at lat. 4°3'N., 

 long. 8i°3i'W., 899 fathoms. The specimen described by Alcock has been taken in the 

 Arabian Sea, 1091 fathoms. 



3. Ser gestes Gardineri Kemp. PI. I, figs. 2a — ie. 



1913. Sergestes gardineri Stanley Kemp, Trans. Linn. Soc. Lond. 2. ser., Zool. Vol. XVI, 

 pt 1, p. 55, PI. 7, figs. 2—5. 



1) Figured in my forthcoming report on the Sergestida: from the "Travailleur" and the "Talisman". 

 SIBOGA-EXPEDITIE XXXVIII. 



