44 AUSTRALASIAN ANTARCTIC EXPEDITION. 



Judging from Mclntosh's remarks, a structure that seems characteristic is a sub- 

 tentacular frontal cone, which he refers to as a " sub-tentacular cirrus " though this 

 term does not seem altogether applicable to such a short conical process. This " frontal 

 cone " is situated between the bases of the palps immediately below the median tentacle 

 (fig. 37). It is quite distinct and separate from the ridge which forms part of the upper 

 lip, and appears to spring from the underside of the prostomium itself. When the 

 median tentacle is absent, as it is in one of the two individuals, this frontal cone is seen 

 projecting beyond the tentaculophore (fig. 36). It is white with a brown base. 

 Mclntosh refers to this " remarkable " organ as being " unique " (p. 93), and in this 

 place does not refer to any other species except some of the Acoetinse as presenting 

 anything like it. Nevertheless on p. 112, in the course of his account of Polynoe platy- 

 cirrus he does mention that a small cylindrical boss occurs in the same position. I have 

 examined a specimen of this species and can confirm this statement, but it has a spherical 

 shape and is by no means so noticeable as in Eulagisca. The use of the word " unique " 

 seems to suggest that it is one of the generic characters of Eulagisca, especially as he 

 gives no diagnosis of this or any of the new genera and sub-genera he had occasion to 

 establish. I do not recall meeting with any reference to such a structure in more recent 

 works dealing with the Polynoids ; yet it is a structure that is so definite that it may have 

 a wider range and be of value in differentiating some of the species of that puzzling group. 



The ventral surface of the worm is colourless, the chaetae are pale brown. The 

 dorsum is marked with very-pale chestnut brown in the median anterior region, and 

 darker on the peristomium. At about -Jrd of the body length, this continuous band of 

 pigment breaks up into a series of irregular patches which get fainter and smaller till 

 about the last quarter, when they die out. 



The prostomium is colourless, though in one specimen it has a crescentic mark 

 of dark brown across each half, which is lacking in the other specimen. There is a 

 small patch of dark-brown on the upper surface of each of the cirriferous segments just 

 within the cirrophore, and in the elytriferous segments a corresponding patch. The 

 dorsal cirri have a ring of very pale brown below the subterminal swelling. The anus 

 is surrounded by a dark-brown area. 



The prostomium is broader than long, has no peaks, and the three tentacles arise 

 in one plane ; the anterior region of each half is continued into the tentaculophore, 

 though in the smaller individual, which is less well-preserved than the larger, each half 

 of the prostomium appears to be produced into an internally directed peak ; but this is 

 due to the oblique line separating it from the lateral tentaculophore. 



The eyes are relatively large, and each is provided with a lens ; the anterior are 

 situated laterally about half-way along the prostomial lobe at its broadest part ; the 

 posterior eyes are dorsal, about half-way between the anterior eye and the hinder 

 margin, though they appear further back in the less well-preserved individual. The 

 hinder margin of the prostomium is over-hung by a forward continuation of the peris- 

 tomium. 



