88 AUSTRALASIAN ANTARCTIC EXPEDITION. 



There is one point on which. Ehlers makes no comment, and that is the fact that 

 Mclntosh states that the stem divides into three and that each of these splits into several 

 branches, whereas in S. spinifera, as figured in 1908, there are only two main branches. 

 Perhaps it is a matter of small importance, but it may as well be referred to here. In 

 one of my specimens one of the two branches divides again soon after its origin, giving 

 the impression of three divisions. Mclntosh's figure shows at least five branches, which 

 I think is an error on the part of the artist. 



(3) " Judging from Mclntosh's figure of the animal, a segment appears to be 

 intercalated between the two segments which bear the lateral ' flaps ' or lobes, and 

 his account is difficult to correlate with the figure." 



Ehlers, in describing his specimen of S. mirabilis, finds no such intercalated 

 segment; the gill is on the 2nd segment, the lateral lobes on the 3rd and 4th as in 

 S. spinifera; the shape of the first flap is similar in the two forms, and is larger than the 

 second flap. 



I have introduced a figure showing more diagrammatically than does Ehlers's 

 figures the real arrangement of these segments. I have little doubt that Mclntosh's 

 figure is misleading. 



(4) Ehlers has noted certain differences in the form of the uncinus as 

 described and figured by Mclntosh for S. mirabilis, and those he himself describes 

 for S. spinifera, in regard to the smaller denticles above the large fang. Mclntosh 

 describes three denticles, but his figure (pi. XXVII A, fig. 34) shows at least four 

 and perhaps a minute fifth. Ehlers in his specimen of S. mirabilis finds a single 

 tooth between the fang and the cap of small denticles, so that the uncinus appears 

 to be three-toothed when seen from the side. In S. spinifera, according to 

 Ehlers, this intermediate tooth is absent. 



In the specimens from Commonwealth Bay, I find a difference from both these 

 accounts, or rather from all three, for instead of there being only one intermediate tooth 

 I find three rows of small teeth, of 2, 3 and 4, or sometimes of 3, 4 and 4 respectively, 

 between the fang and the cap of minute denticles (fig. 100). In a side view (fig. 99) the 

 uncinus is more like the figure of one of " the anterior hooks " given by Mclntosh than to 

 the figure illustrating Ehlers's account. 



Some further points of comparison may be made. 



The dimensions of the worms have perhaps little value in deciding their identity, 

 yet they may be included in this analysis. Ehlers's type of S. spinifera was imperfect ; 

 but in 1913 he gives the dimensions of a complete individual. 



Body Diameter. Number of 



length. segments. 



Ehlers 105 6 134 



Gravier 75 91 



"Aurora" 70 7 90 



<S. mirabilis Mclntosh 58 2 



