264 A HISTORY OF EECENT CRUSTACEA 



amon^ preserved specimens of Eupliausiiclse. The two coni- 

 cal ovisacs, placed side by side between the last two pairs 

 of appendages of the trunk, ' do not consist of iDcubatory 

 lamellag, as in other Schizopoda, but merely of an exceed- 

 ingly thin membrane, derived, it would seem, from some 

 glutinous fluid issuing along with the ova and coagulated 

 by the action of the sea-water as a delicate envelope sur- 

 rounding and keeping the ova together during the em- 

 bryonal development.' The curious fact is noticed that of 

 the northern species the specimen of Nycti2')hanes Couchii 

 figured by Bell in his ' History of British Crustacea ' is the 

 only ovigerous one that has as yet been recorded. 



Be)it/ieuphausiaj Sars, 1885, has all the legs distinctly 

 developed, and though the last pair are rather short, they 

 have both branches of a structure similar to that of the 

 preceding pairs. The single species, BeiitJieupJumsia 

 amhlyops, Sars, has small and imperfectly developed eyes. 

 The three specimens on which it was founded were taken 

 from depths between 1,000 and 1,800 fathoms, and appear 

 to be devoid of the luminous globules found in so many 

 other members of this family. 



21iysano6Ssa, Brandt, 1851, has the last pair of legs quite 

 rudimentary, and the preceding pair exceedingly small, 

 devoid of the three terminal joints. On the other hand, 

 the second maxillipeds are very elongate, much longer 

 than the following legs. They have the last two joints 

 armed with spiniform bristles on both margins. The 

 eyes in this genus are of a somewhat irregular form, with 

 the cornea divided, as it w^ere, into two compartments by 

 a transverse constriction. The tyj^e species, Thysaiioessa 

 loncjvpes, Brandt, from the Siberian Sea, is identified by 

 Norman with the earlier Thysanopoda nefjlecta, Kroyer. 

 Sars lias added a southern species, Thysanoessa macrura ; 

 a wide-ranging species, Tlrysanoessa ^m/ttW«, which is found 

 in the Mediterranean ; and two from the coast of Norway, 

 which he has named horealis and tenera. Dr. H. J. Hansen, 

 however, having examined Kroyer 's specimens in the Co- 

 penhagen Museum, has come to the conclusion that 

 Thysanoessa horealis^ Sars, should be called Thysanoessa 



