30 AUSTRALASIAN ANTARCTIC EXPEDITION. 



The transversely extended prostomium (figs. 9-10) bears the usual large eyes, 

 arranged as in the Sacconereis. Springing from the upper surface near the hinder 

 border is the long median tentacle, which is about 5 mm. in length. The lateral 

 tentacles are noticeably larger, being about twice the thickness of the median and of 

 greater length. That region of the prostomium from which they arise has apparently 

 been pressed backwards and downwards, so that the peristomial cirri appear, in dorsal 

 view, to be in front of them. Below the base of these long lateral tentacles is a large 

 swollen subspherical mass overhanging the chsetigerous lobe of the second segment. 

 It is upon this mass that the lateral tentacles stand. 



From the anterior margin, between the eyes, the club-shaped " frontal tentacles " 

 arise, and below them the " bifurcated appendages " (which according to Malaquin 

 represent the united palps and lateral-anterior tentacles, a view that Ehlers does not 

 accept). I prefer to use the above term so as to avoid any morphological controversy. 

 These " bifurcated appendages " consist of a thick basal region which divides into two 

 branches, one shorter and thicker and fleshy; the other longer and slenderer. The 

 former appears to be a continuation of the basal region (than which it is rather longer), 

 and so to constitute the main axis ; the latter branch is borne on the under and outer 

 face of the fleshy portion; it is about |rd the length of the median tentacles, but as both 

 are coiled, it is difficult to give precise measurements. 



These organs spring from the prostomium below the frontal tentacles at a level 

 of a line drawn across between the dorsal and ventral pairs of eyes : their bases touch 

 ventrally. Their position on what appears to be the morphological dorsal surface of 

 the prostomium seems to negative the view that they are palps unless their origin has 

 shifted upwards, as that of the lateral tentacles has shifted downwards. 



Both the basal region of the appendage and the thicker branch are IT arked by 

 a series of granular rings from which spring hairs, some of which in a mounted specimen 

 are curved. Presumably they are sensory hairs. Unfortunately they are invisible in 

 Canada balsam mounts, though clearly seen in glycerine preparations. 



The ailerons or epaulettes are present, extending across the bases of the large 

 tentacles and, as in the atokous phase, reach to the hinder end of the third segment. 



In some specimens, but not in all, there is a linear white ridge passing backwards 

 from the prostomium in the middle line over the first six or seven segments. I noticed 

 it both in large and small individuals, in dark and in pale ones, while in others it is not 

 present. I failed to detect it in the Sacconereis. Although visible in reflected light 

 it is not to be seen in any of the mounted specimens. Has this low linear ridge anything 

 to do with the " birnformig Hocker," which Ehlers describes and figures for this 

 Pterautdytus (1907, p. 8). This is a small pear-shaped upstanding structure on the 

 mid-dorsal line of the 2nd segment. On p. 10, he compares it with certain " occipital 

 Hocker " which occur in some other syllids, such as Syttis notocera Ehlers and Autolytus 

 gibber Ehlers; in the latter, however, it is merely a broad round-edged lobe overhanging 



