COPEPODA. 31 



Second feet, Ri distinctly two-jointed. 



Third and fourth feet, Ri and Re of three joints each, 5 2 of the fourth feet with 

 tubal bristles as in Gaidius. 



The extraordinary size of this animal makes it the largest known species of 

 Gaetanus. It occurred once only in the ' Discovery ' collection, and also appeared in 

 the ' Gauss ' collection , and is probably Antarctic in its habitat. Several new species of 

 Gaetanus have been described recently, and it may serve some useful purpose to 

 recapitulate here the different species discovered since Giesbrecht and Schmeil's last 

 work (Tierreich, 1898). 



1. Gaetanus major. 



6. major, Wolfenden, Proc. Zool. Soc, London, Feb. 3, 1903, in Dr. Fowler's paper. 

 „ Farran, Ann. Rep. Fish. Ireland, 1902-03, Part II., App. II., 1905. 



Size 5 mm. and over. Anterior antennae larger than the body by about one joint ; 

 lamellar appendage of posterior foot jaws absent ; Re of first feet of three segments, 

 and with three Se. Cephalic spine short, and as in G. armiger. 



2. Gaetanus caudani. 



Gaetanus caudani, Canu, Ann. Univ. Lyon, V. 26, 1896. 



„ Wolfenden, Jonr. Mar. Biol. Assoc, 1904, p. 24. 

 ,, (?) pileatus, Farran, ibid. 



Like G. miles, but anterior antennae only one-and-half times as long as the body ; 

 lamella of posterior foot jaw like that of G. miles. Re of first feet, three segmented 

 basals of fourth feet with tubal bristles, 5 mm. and over. Canu's original description 

 was of one immature 6 . Farran's were also immature specimens. 



3. Gaetanus holti. 



Gaetanus holti, Farran, ibid. 



„ latifrons, Sars, Bull. Mus. Monaco, No. 26, March, 1905. 



longispinus, Wolfenden, Plankton Studies, Part I. (1905), p. 7. 



Cephalic spine strong and directed backwards with long interval between the 

 frontal part and base of the horn. Anterior antennae not as long as the body-spines of 

 the last thoracic segment, strong, long, and directed backwards. Small lamella on 

 posterior foot jaw. First feet with three segments and three Se. Fourth feet with 

 basal tubal bristles. Size 4 • 74 mm. 



4. Gaetanus antarcticus. 

 Gaetanus antarcticus, Wolfenden, Plankton Studies, Part I. (1905), p. 7. 



Thorax gibbous, very stout short curved cephalic spine directed forwards, head 

 square, not like G. armiger. Abdomen short and thick, not a quarter of whole length. 



