EEPOET ON THE PTEEOPODA. 27 



suckers is nearly that of a fiat porringer with a rather narrow edge ; the largest are 

 about one line in diameter. 



Radula. — Formula 6:0 : 6. 



Hook-sacs very long. 



Colour. — -Violet brown, more or less dark (Costa 1 describes this species as red 

 coloured). 



Length. — The adult specimens measure 17 mm. 



Habitat. — Mediterranean Sea (Naples, Messina, Nice) ; according to Boas, 2 this species 

 is also to be found in the Atlantic Ocean, and in the China Sea. 



Observations. — Contrary to the opinion of Boas, I consider the species with seven 

 suckers, obtained frequently at Naples (and which he designates Pneumodermon macro- 

 cotylum), as identical with the species from Nice, formerly described by van Beneden as 

 Pneumonoderma rnediterraneum ; I therefore think that the latter name must be retained 

 for it. 



Boas identifies his Pneumodermon macrocotylum with " Pneumodermon rnediter- 

 raneum" Gegenbaur, which he consecpiently distinguishes from van Beneden's species. 

 But Gegenbaur 3 says : — "Acetabula five or six"; and van Beneden's figures 4 also show 

 the same number of suckers (five or six) . 



The suckers in van Beneden's figures really appear smaller than those of a well- 

 preserved Pneumonoderma from Naples ; but in very contracted specimens (as those of 

 van Beneden), the shape of the suckers is altered and they seem smaller. 



I have already said that the Mediterranean Gymnosomata are not yet well known. 

 Gegenbaur observed a " Pneumodermon violaceum " " more common at Messina, during 

 autumn, than Pneumodermon rnediterraneum" and bearing from ten to fourteen 

 suckers on each buccal appendage. This form, of course, differs from Pneumonoderma 

 violaceum, d'Orbigny, and has not since been seen in the adult state. Boas 5 has found 

 some larvae from Messina bearing ten or eleven suckers on each appendage, and these 

 undoubtedly belong to the species Pneumonoderma violaceum of Gegenbaur. 



Up to the present time adult Pneumonodermata have only been found in the 

 Mediterranean, at Naples, Messina and Nice. But they must also live in other parts of 

 this sea, since larvge have been found at Malaga (Trizonius csecus), by Busch, 6 and in the 

 Adriatic sea, at Trieste, by Johannes Midler. 7 



1 Pteropodi della fauna di Napoli, p. 22. 



2 Spolia atlantica, p. 153. 



3 Untersuclmngen uber Pteropodeii und Heteropoden, p. 213. 



4 Loc. cit, p. 213. 



6 Spoiia atlantica, p. 151. 



6 Beobaebtungen iiber Anatomie und Entwicklung einiger wirbellosen Seetbiere, p. 112. 



7 Ueber verschiedene Formen von Seetbiere, Archivf. Anat. u. PhysioL, p. 69, 1854. 



