ON PTYOHODERA FLAVA. 1G5 



On Ptychodera flava, Eschscholtz. 



By 



Aithiu- Willey, D.Sc. 



With Plate 5. 



Ptychodera flava has the distinction of being the oldest 

 as well as one of the least known of the Enteropneusta, having 

 been recorded and figured for the first and only time by 

 Eschscholtz in 1825, from material obtained from the Marshall 

 or Rumanzow Islands, in the Pacific, north of the equator. 



Eschscholtz, as quoted by Spengel,^ regarded his Ptychodera 

 as a worm-like animal belonging to the group of the Holo- 

 thuridae. Otherwise, however, his description was very de- 

 fective, and far from being a specific diagnosis. Still, in so 

 far as Eschscholtz stated that the body of the animal was " der 

 Lange nach gespalten,'^ and also from the figure which accom- 

 panied his description, and is reproduced in Spengel's mono- 

 graph, indicating the presence of genital pleurae (see below), 

 Spengel was enabled to retain the species in his amended 

 genus Ptychodera. 



Since 1825 this species has not been re-discovered in the 

 true sense of the term, although Spengel makes the suggestion, 

 which the present contribution provisionally" supports, that 

 the fragments of a Balanoglossus obtained by Dr. Fran9ois in 



' J, W. Spengel, " Die Enteropneusteri des Golfes von Neapel, &c.," 

 ' Fauna und Flora des Golfes von Neapel,' Berlin, 1893. 



^ I say provisionally because absolute certainty can only be arrived at 

 when the form from the first recorded habitat (Marshall Islands) comes to be 

 re-investigated. 



