ATLANT. DEEP-SEA EXPED. 1910. VOL. HI], 



SCYPHOMEDUSAE. 



13 



Vanhoffen 1 ) who has had the opportunity of studying 

 a large amount of material, separates the species according 

 to the presence or absence of radial furrows on the central 

 disc, A. Verrilli having radial furrows, while A. Bairdl has 

 a smooth central disc. The radial furrows are generally 

 rather indistinct, and in a note Vanhoffen admits that 

 in larger specimens they disappear almost completely "so 

 dass nur am Rande ihre Spuren erkennbar bleiben und 



According to the radial furrows we can separate three 

 groups among the specimens. First, those furnished with 

 distinct radial furrows all over the central disc, second, 

 those with incomplete radial furrows, in many cases visible 

 only at the margin of the central disc; and third, those 

 with a perfectly smooth central disc, showing no trace 

 whatever of radial furrows. The first group comprises 

 almost one-third of the material, and the last group less 



Atolla Bairdl. 



Depth 

 (metres) 









Diameter of disi 



: (millimetres) 





Total 



7-10 



11—20 



21—30 



31—40 



41— 50 51— eo 



61—70 



71—80 



81 — 90 J 91—100 



101 — 110 



250 



1 



_ 





















1 



500-550 



750 

 1000-1100 



1250 

 1500—1600 



3 



2 

 6 



7 



9 



21 



2 

 8 

 9 

 2 

 1 



1 

 2 

 5 



1 



2 

 1 



3 

 1 



1 



1 

 1 











1 



2 



17 

 27 

 45 

 2 

 10 



— 



4 



2 



1 



— 



— 



1 



1 



— 



— 



20C0 



— 



— 



1 



— 



— 



— 



— 



— 



— 



— 



— 



1 



Total 



12 



41 



' 23 



10 



5 



5 



2 



1 



1 



1 



2 



103 



Atolla Verrilli: 



Depth 

 (metres) 



500 

 750 

 1000 

 1200—1250 

 1500 



Total 



Diameter of disc (millimetres) 



10-20 21—30 31—40 41—50 51—60 61—70 71-80 81-90 91—100 



7 

 2 

 13 

 2 

 3 



27 



1 



Total 



9 

 21 



8 

 11 



57 



Fig. 7. Table showing the bathymetrical distribution of the different sizes in the "Michael Sars" specimens of 

 Atolla Bairdi and A. Verrilli. The figures denote number of individuals. 



solche Stucke der A. Bairdl sehr ahnlich werden." Maas 2 ) 

 also states: "Les exemplaires captures par le Prince 

 de Monaco se rapportent a une seule espece, A. Bairdl 

 Fewkes, mais dans quelques uns (stn. 1269), on croit 

 reconnaitre avec de la bonne volonte des traces des fosses 

 radi'aires sur l'ex-ombrelle, on pourrait alors penser aussi 

 a A. Verrilli, qui certainement est une espece tres voisine." 

 And if we examine the figures of A. Bairdl by Fewkes 3 ) 

 we find the furrows of the central disc distinctly indicated 

 at the margin; we might say that they represent the half- 

 disappeared radial furrows of large A. Verrilli according 

 to Vanhoffen. 



The limits between these two species are by no 

 means distinct, but the investigation of the "Michael Sars" 

 material has in several ways solved the problem. 



so that most of the specimens belong to the intermediate 

 group. The question arises whether these intermediate 

 specimens are to be referred to A. Bairdi or to A. Verrilli. 

 If these individuals were all large, we ought to follow 

 Vanhoffen in referring them to A. Verrilli, but the per- 

 centages of large and small individuals are the same in 

 each of the three groups. The intermediate group contains 

 every transition stage from A. Bairdi to A. Verrilli, and 

 we are therefore compelled to consider A. Vertilli as a 

 synonom of A. Bairdi. 



But should A. Verrilli not be retained as a separate 

 form? First of all we must make it clear what is required 

 ot groups of specimens or of variants if they are to be 

 considered separate "forms". In reality we have two 

 different kinds of forms. 



1 ) Deutsche Tiefsee-Expedition, p. 8. 



2 ) Meduses provenant des Campagnes des yachts Hirondelle et Princesse Alice (Res. Camp. Scient. Prince de Monaco. 

 Fasc. XXVIII), Monaco 1904, p. 49. 



a ) Rep. Medusae Gulf Stream, pis. I, II and IV. 



