NEMERTEA ENOPLA 



631 



sub-orders exists in the length of the proboscis sheath, which 

 in the first group is developed in part of the body only, in the 

 Holorhynchocoelomia, however, is present from the snout to 

 the tail. That this division is unnatural Brink mann 

 showed in his monograph on the pelagic Nemerteans (4). 

 In this most interesting paper, that contains the minute 

 anatomical description of eighteen genera of pelagic Nemer- 

 teans with thirty-two species, the greater part of which are 

 new, Brinkmann describes nearly related species of one 

 genus, Balaenanemertes, that might be types of Biirger's 



Text-fig. 3. 

 rhynch w. 



cCfx conxm.. 



I I 1 1 I I I I I I 1 1 I I I I I I I" I i / -r-r- 



Schematic longitudinal section of Malacobdella grossa after 

 Biirger (6, PI. xviii, fig. 2). 



two sub-orders. In other genera the difference is less great but 

 still exists. This fact alone is sufficient to demonstrate the 

 unnaturalness of the subdivision of Burger's Metanemertini. 

 Another fact of interest was that all pelagic forms are nearly 

 related, and show a peculiarity in the armature of the proboscis 

 that we knew only from the genus Drepanophorus. This 

 genus is one of Biirger's Holorhynchocoelomia. Though 

 at' first included in the family Amphiporidae, the family 

 Drepanophoridae was later established; and Biirger 

 believed this genus with its paired rhynchocoelomic diverticula 

 to be the most highly specialized one of his sub-class. In his 

 shidy on Uniporus, a nearly related genus, Brinkmann (3) 

 came to the conclusion that the Drepanophoridae in many 

 respects are very primitive forms of Hoplonemerteans, which 



