72 DR. H. J. HANSEN ON CRUSTACEANS. [Jan. 20, 
Pacific. S. atlanticus H. Milne-Edw., S. edwardsti Kx., S. vigilax 
Stimps., H. J. H., 8. tenwiremis Kr., H.J. H., and S. corniculum 
Kr., H. J. H., have been proved to be distributed through the 
tropical and subtropical parts of the Oceans almost around 
the globe, viz., from lat. 23° N., lat. 32° N., or even lat. 42° N. 
in the Atlantic, throughout the Indian Ocean to Australia, New 
Hebrides, and “South Pacific.” 
III. Luminous Organs im Sergestes challengeri, n. sp. 
(Plate XII.) 
The luminous organs briefly mentioned above are generally 
easy to discover; each resembles a very convex, vitreous, faintly 
yellowish lens, which is circular and sharply defined. They differ 
much in size, some of them being very small and many pro- 
portionately large. It may be advisable, first, to give a con- 
spectus of the organs observed on the single and unfortunately 
very mutilated specimen, next to add some remarks on their 
distribution, then to describe their structure, finally to compare 
them with luminous organs in other Crustacea. 
Conspectus of the Organs observed. 
Organs. 
On each side of the scutum a row with four organs. 8 
Omitherclypeus one organi rece tee leper ee eee eeeEer 
On the lower side of the head one unpaired organ 
and one near the lateral margin.................. 3 
On the lower surface of the thorax and on its infero- 
lateral amano Sip.sec ie cicinde uae eeeeteck eee eeny eee 26 
On the lower side of the third joint of the antenn. 
[QOL OLS) WIAA SH coh adadoos4un oHsosodosobosoGCoHADE +: 
On the lower side of each squama four organs ...... 
On the mandible and its palpus two organs ......... 
On the first maxilliped two organs..................... 
On the second maxilliped five organs .................. Ih 
On the first trunk-leg three organs .................. 
On the lower surface and on the lateral wall of the 
firstiabdominaliseamlentipree.asscen---eeee eee eee 
Do., do. of the second abdominal segment ............ 
Do., do. of the third abdominal segment ............ 
Do., do. of the fourth abdominal segment............ 
On the lateral wall of the fifth abdominal segment. 
Along the median line of thesixth abdominal segment. 
On the outer side of the basal joint of each of the 
pleopodsiomejorsamyten cena: cpiieiyieee an eer eee 
On the peduncle and on the inner branch of each 
VEO} COLO IO) CLAZENAS, "Sodan quads sasecouscsogonoeosococ 4 
On the lower side of the outer branch of each uropod 
UV OROLESIINS 655 4NG soc an dgd CoGuaRREROOa y yanooEaoCaseod 75 4 
AO, FS Or 
or ES Sermon) 
— 
(=) 
Total number of organs ... 117 
