Proximal widened part of the telson with a single pair or, most frequently, two pairs of marginal 

 spines ; spines along almost the distal fourth or the distal third of the lateral margins of the 

 telson increase regularly (in 5. quadrispinosa not quite regularly) in length backwards. The 

 rami of fourth (and third) pair of male pleopods subsimilar in length, with all their distal sets 

 normal as on the other pairs. Pseudobranchial rami of second to fourth pairs of male pleopods 

 spirally twisted. 



12. Siriella Thompsonii H. Milne-Edw. 



1837. Cyntlüa Thompsonii H. Milne-Edwards, Hist. Nat. des Crust. T. II, p. 462. 



1852. ? Siriella vitrea Dana, U.S. Expl. Exped., Crust. I, p. 656, PI. 43, figs. 6a — 6;«. 



1852. 'rSiriella brevipes Dana, U.S. Expl. Exped., Crust. I, p. 658, PI. 44, figs. \a — \q. 



1S61. Cynthia inermis Kröyer, Nat. Tidsskr. 3. R. B. I, p. 44, Tab. II, Fig. 6, a — g. 



1868. Siriella Edivardsii Claus, Zeitschr. wiss. Zool. B. XVII, p. 271, Taf. XVIII. 



1882. Siriellides indica Czerniavsky, Mon. Mysid. I, p. 103, Tab. XXXI, figs. 1 — 6. 



[885. Siriella thompsoni G. O. Sars, Challenger Rep., Vol. XIII, p. 205, PI. XXXVI, figs. 1 — 24. 



Stat. 96. June 27. South-east side of Pearl-bank, Sulu-Archipelago. 15 m. Surface. 14 specimens. 



Protosiriella Thompsoni Czern., Siriellides Edwardsi Czern., Siriella inermis Czern. 

 and Siriella vitrea Czern. are synonyms to the same species, but Czerniavsky only copied 

 descriptions from earlier authors, erroneously considering their imperfections as characters of 

 different species. 5. vitrea Dana is either identical with 5. Thompsonii or unrecognisable; 5". 

 brevipes is possibly an immature 5. Thompsonii; at all events both ought to be cancelled. — 

 Whether Promysis Galathece Kröyer belongs to this species cannot be decided; it will even for 

 ever be impossible to recognize the form from Kröyer's description and figures as his type 

 specimen is lost, wherefore the species ought to be cancelled in the literature as unrecognisable. 



Remarks. — G. O. Sars has given an excellent representation in the "Challenger" 

 Report of this widely distributed species, which has been taken at the surface in all tropical 

 and warmer temperate parts of the Oceans. It agrees with 5. gracilis Dana but differs from 

 all other species hitherto established or seen by me by the feature that the endopod of the 

 uropods conspicuously overreaches the exopod ; the latter has 3 to 6 marginal spines. The 

 antennal squama is narrow, at least about five times as long as broad. 



13. Siriella gracilis Dana. 



1852. Siriella gracilis Dana, U.S. Expl. Exped., Crust. I, p. 658, PI. XLIV, figs. la—ig. 

 1S85. Siriella gracilis G. O. Sars, Challenger Rep. Vol. XIII, p. 209, PI. XXXVI, figs. 25— 28. 



Stat. 35. March 28. Lat. S°o'.3 S., long. ii6°5q'E. 1310 m. Plankton, surface. Large number 



of specimens. 

 Stat. 37. March 30/31. Sailus ketjil, Paternoster-islands. 27 m. and less. Plankton, surface. 



1 specimen. 

 Stat. 66. May 7/8. Bank between islands of Bahuluwang and Tambolungan, south of Saleyer. 



8 — 10 m. Plankton. 24 specimens. 

 Stat. Si. June 14. Pulu Sebangkatan, Borneo-bank. 34 m. Plankton. 32 specimens. 

 Stat. 96. June 27. South-east side of Pearl-bank, Sulu-Archipelago. 15 m. Plankton, surface. 



Large number of specimens. 



