SYSTEMATIC AND BIOLOGICAL ACCOUNT 55 



The gastrozooids of C. sarsii appeared pink as the animals were carried along in the ebb tide off 

 the pier at Valentia Island. Further observations on the pigmentation of this species are desirable. 

 At times it is abundant at Valentia Island. 



Marrus gen.n. 



Type species Marrus antarcticus sp.n. 



Holotype (in fragments) from 'Discovery II' Station 943 



Species of this genus are known from fragments only. The lateral radial canals are unlooped, the 

 tentilla are unicornuate. 



Marrus antarcticus sp.n. 



I have named the new genus to which this large Physonect from antarctic and southern sub- 

 antarctic waters belongs after Mr J. W. S. Marr, who has had more than thirty years active association 

 with the Antarctic and has always treated siphonophore material with loving care. He also made 

 useful colour notes on this Siphonophore when it was alive. It appears to be closely related to a species 

 ' Stephanomia' orthocanna from deep cold water in Baffin Bay described by Kramp in 1942, and since 

 collected by 'Scotia' at Station 688 in 1951 at 1100 m., some 5 W. of the south-west end of the 

 Faroe-Shetland Channel. 1 Through the kindness of Kramp I have been able to compare nectophores, 

 stems and siphons. The nectophores of both have straight lateral canals and their other details are 

 very similar. The siphons of both have a long, cylindrical basigaster, and are in other respects similar. 

 Unfortunately, the northern specimens, whose stems show numerous attachments of bracts, were 

 not associated with either attached or unattached bracts except for one specimen which had one small 

 attached one. As described by Kramp, the bract is of a different shape from those so characteristic 

 of Marrus antarcticus. The specimens of the northern form had very few tentilla, so that a satisfactory 

 description of them has not yet been made. 



Description. Nectosome at present known only from loose nectophores. Nectophores measuring 

 uptoi7Xi5X9 mm., lateral facets triangular but not cut off by an oblique cross ridge; two broad 

 lateral wedges, and broad median lappet (thrust block) ; dorso-lateral ridge bifurcated distally. These 

 ridges are present, though not easily seen except after staining, also in 'Stephanomia' orthocanna, but 

 not figured by Kramp. Nectosac lacks musculature on its broad basal (adaxial) face as in' S.' orthocanna. 

 The blind end extends in the form of two widely rounded lateral arms; lateral-radial canals unlooped. 

 Siphosome long, coiled in tight turns when preserved, apparently unsegmented, about 6 mm. in 

 diameter when contracted and preserved. The appendages are all budded from the ventral, non- 

 muscular groove. Gastrozooids of a specimen from 'Discovery II' Station 2010, reached a length 

 of 30 mm., of which about half is the cylindrical basigaster. Another gastrozooid (St. WS 552 E) 

 measured 27 mm., the basigaster accounting for 5 mm. It was dilated with food at the distal end 

 which measured 5 mm. in diameter. A third gastrozooid, 15-5 mm. in length, from the same 'William 

 Scoresby' Station 552 E consists of three parts: (1) the basal, cylindrical basigaster, which measures 

 6-omm. in length and i-omm. in diameter; (2) the stomach proper with 'liver streaks', which 

 measures 7-25 mm. in length and 1-25 mm. in diameter; and (3) the oral section (closed) which 

 measures 2-25 mm. in length and 0-5 mm. in diameter. Mature tentilla are unicornuate, have no 

 involucrum and a simple, straight canal. The pedicel of a retracted tentillum measures about o-8 mm., 

 the cnidoband, in three coils, 0-9 mm. and the filament 1 mm. in length. A more extended tentillum 



1 Dr J. H. Fraser of the Scottish Fisheries Department has been kind enough to inform me that evidence from hydrographic 

 data as well as from planktonic data would suggest that there is very little outflow, if any, into the Atlantic through the 

 Faroe-Shetland Channel even in deep water. He thinks that it is much more likely that 'S.' orthocanna and other cold-water 

 plankton species taken in haul S 51/688 had penetrated southwards via the area west of the Faroes than through the channel. 



