92 AUSTRALIAN SYLLIDAE^ EUSYLLIUAE AND ArTOIATIUAE, 



CompaiativL'l}- rare are specimens in which, though the dorsal surface is 

 darkly pigmented, it wants the characteristic pattern described aI)o\e, the pigment 

 being disposed in transverse bands, lr\vo on each segment; here too there is an 

 alternation of darker and lighter segments with the alternation of the shorter 

 and longer cirri. 



^lany of the smaller specimens however, are devoid of the dark pigment. 

 Many of these have a light red colour due to the presence of diffused particles 

 of red pigment, some are gTeenish, others orange or yellow. 



Apart from markings and colouration, the following points seem to be dis- 

 tinctive of a. varieyata: — 



Palpi in the living animal elongated, lo-iger than the prostomiuni, their inner 

 edges in contact at the base for about a fourtli of their length, narrowing distally 

 with rounded ends, with a deep hollow on the inner part of the ventral surface. 

 Tentacles and cirri elongated, with numerous well-defined segments filled with 

 twisted unicellular (vermiculate) glands. Dorsal cirri alternately longer and 

 shorter, with from twenty to thirty-five segments. The anal cirri are simOar to 

 the dorsal : between them is a median narrow process . 



As in other species of Si/llis, the i:iara podium, when viewed from above or 

 below, though not deeply cleft, appears divided into two lobes at the end. In 

 anterior or posterior view these lobes are found to represent broad vertical Haps, 

 anterior and posterior. Close to the latter on its dorsal side are the points of 

 the acicula; between the flaps or lobes is the irregular surface through which Ihe 

 s?tao protrude. 



The compound setae (Plate x., fig. 1) 8 (o 12 in number in each parapodium, 

 are of uniform character throughout; they all have the appendage (falx) straight, 

 bidentate terminally, and with a strong fringe of some 20 pieces along the cutting 

 edge of the blade. 



The length of the falx is greater in the setae of the anterior region of the 

 body than in those of the segments behind, but the difference is not great, and the 

 transition from one form to the other is very gradual. 



As pointed out by Augener, each parapodium in the extreme posteiior region 

 has, as in most species of SylUs, a simple seta in addition to tht compound. This, 

 which is always dorsal to all the latter, is in ,s'. var'ieguta of the gently curved, ter- 

 minally bidentate type which is the commonest foim of these simple setae in tlie 

 majority of the sijecies of Syllis which 1 have seen. The acicuhi (Plate x., tig. 2) 

 arc fairly characteristic. Usually there are three in each parapodium; hut 

 sometimes there are four or five. When three are present one — the most anterior 

 and ventral — is almost always very slightly l;ent at the end, and slightly knobbed ; 

 the other two, which are very stout, are straight to the end and olrfusely or 

 acutely pointed. 



The position o! the parts of tlie i)roboscis in the usual iTlraclcd state is 

 usuiiUy regarded as important in the diagnosis of -the species of Si/llis: it is 

 fairly constant in the individuals of a species, but is subject to some modification 

 owing to the occasional occurrence of states of incomplete retraction . More im- 

 portant is the loifjih of the pharynx and jnoventriculus in terms of the number 

 of segments through wliich each runs. Within a limited range of variation this 

 appears to be constant for each species — except in (h<' coiniinvntivcly rare in- 

 ^tanees of regeneration. 



In S. variegata both iiharynx and iirovciitiicuhis arc comparatively long, each 

 running througli eight. Iwolvc oi- fourteen segments. 



