256 bulletin: museum of comparative zoology. 



Gonionemus pelagicus, sp. nov. 



Plate 4, Figs. 12, 13, 14. 



The bell is rounded, but low and thin. It is about twenty mm. in diameter, 

 and one third as high as broad. There are about fifty long, straight, flexible 

 tentacles, each of which forms a slight elbow near the tip, in the manner char- 

 acteristic of the genus. These elbows, however, are so inconspicuous in life 

 that the tentacles resemble Melicertum rather than Gonionemus. At the elbow 

 each tentacle bears a small almost rudimentary sucking disc, and they are 

 ringed throughout their whole length. At the base of each there is a cluster of 

 brown pigment spots. There are sixteen otocysts. 



The proboscis is flask-shaped, nearly as broad as long. It is exceedingly 

 flexible, but cannot be retracted. The mouth bears four fimbriated lips. The 

 gonad.s, which occupy the distal third of the radial canals, consist of simple 

 papilliform processes closely crowded together, as in Gonionemus murbachi, 

 from Woods HoU, Mass. 



The bell is colorless: the proboscis and tentacles are yellowish green, the pig- 

 ment spots at the bases of the tentacles Vandyke brown, and the gonads rose 

 pink. 



In life this Medusa bears little resemblance to other species of Gonionemus. 

 It swims freely by frequent contractions of the bell, the tentacles streaming 

 behind at full length. The flexible tentacles are continually contracting and 

 expanding and swaying to and fro in the water. The Medusa showed no incli- 

 nation to attach itself, nor did it swim to the surface, sink, and then swim up 

 again in the manner so characteristic of the genus. The anatomical structure 

 of the tentacles also points to this habit of life, which has led me to give it the 

 name " pelagicus." It differs from all other species of Gonionemus, to which 

 genus it certainly belongs, in the rudimentary condition of the sucking discs. 

 One specimen, January 7, near Gadu island, Suvadiva atoll, surface. 



Messonema coerulescens Brandt. 

 Brandt, 1838, Mem. Acad. Imp. St. Pe'tersbourg, ser. G, vol. 4. 



A single specimen of Messonema was taken on January 8, in Haddummati 

 atoll. It probably belongs to this species, but was too fragmentary for 

 accurate determination. 



Rhopalonema typicum Maas. 



Homoeonema typicum Maas, 1897, Mem. Mus. Comp. ZoiJl., vol 22, p. 22, taf. 3. 

 Two specimens of this species were taken on January 8, in Haddummati atoll. 



