SYSTEMATIC AND BIOLOGICAL ACCOUNT 



59 



Marrus orthocannoides sp.n. 



A haul of the young fish trawl from 1400 to 700 m. at 'Discovery II' Station 1585 in the West 

 Tropical Indian Ocean contained loose nectophores (Text-figs. 22, 23), bracts and denuded stems 

 (nectosome and part of siphosome) of a new Physonect that appears to be closely akin to the high-arctic 

 species ' Stephanomia' orthocanna Kramp. Dr H. Bargmann of 'Discovery Investigations ' has kindly 

 made an approximate estimate of what would have been the temperature and salinity reading at the 

 time and place of capture. Her figures are : 



_ A-C.ped 



C.radd 



Crad.v. 



-Cradlat 



C.ped 



Text-fig. 22. Marrus orthocannoides sp.n. Upper and side views of a nectophore 

 from 'Discovery II' St. 1585, 1400-700 m. x 6. 



I have already described (p. 55) a new antarctic Physonect which appears, in the present state 

 of our knowledge, to be congeneric with 'S.' orthocanna, and owing to the fact that, since the name 

 ' Stephanomia ' is used in a loose way for a number of macrostele Physonects, whose tentilla have single 

 terminal filaments, these three species have been placed in the new genus Marrus. The study of each 

 of these three related species has been difficult because of the fragmentary condition of the material. 



The nectophores of the three related species are characterized by the absence of any oblique ridge 

 dividing the lateral facets. On the dorsal surface there is a pair of ridges dividing it from the lateral 

 surface. Each divides again before reaching the ostium of the nectosac. These ridges are not shown 

 in the figures by Kramp (1942) of ' Stepha?iomia' orthocanna, but, after staining a nectophore kindly 



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