POLYCH.ETA FROM NORTH AAIERICA. 797 



ascending variety in some localities is much more common than 

 the discoid one, and it grows to a much larger size (fig. 8 b), often 

 attaining a height of 5 mm. It was generally found with its 

 lower coils overgrown with an orange Bryozoan growing on 

 Ghcetopterus tubes. 



The living animal had a reddish colour, with a colourless ti-ans- 

 parent operculum. A string of pink ova extended along the tube 

 beyond the posterior end of the body in some specimens. There 

 Avere 3 thoracic and from 12 to 20 abdominal segments. 



The collar setae attain a length of '27 mm., much larger than 

 those figured by Caullery & Mesnil (5. fig. 4 5), they resemble 

 more closely in shape those given for S. armor^icanus (5. fig. 5 h). 



The ditterences between these two species were pointed out 

 by Caullery &, Mesnil (5. p. 199) to be quite unimportant. All 

 that they could summarise were that 8p. armoricanus (Circeis 

 armo7-icanus St.- Joseph (24. p. 350)) was slightly larger, had more 

 abdominal segments (16-20) and a reduced talon to the operculum. 

 They record having seen intermediate forms themselves, and the 

 above observations as to variation in size, the number of abdom- 

 inal segments, and the collar setaj conseqviently confirm their 

 opinion that Sp. armoricanus should be considered as a variety 

 only of Sjy. spirillum,. 



9. Spirorbis pusilloides Bush (3). (PI. LXXXVIII. figs. 9«, 



9 b \ 

 S. pusillus Caullery & Mesnil (5), 1897. *^ 



Mera pusiUa St. -Joseph (24), 1894. 



Xon S.2ncsiUas Ilathke (22 a), 1836. 



Specific characteristics : — 



1. Collar setfe of a more or less geniculate form (fig. 9 a). 



2. Embryos incubated in operculum. 



3. Seta? of 3rd thoracic segment sickle-shaped. 



4. Hepatic pigment reddish brown. 



On stones from Taylor's Bay, Cabriole Island. This animal 

 agrees in all important points with the full description by 

 St.-Jos3ph (24. p. 351) for Mera jjusilla. The collar setee are a 

 little more distinctly angulated at the base of the blade (fig. 9 a), 

 but they have not the typical geniculate form described by 

 Caullery & Mesnil (5. p. 202). They are much shorter than 

 the setae of the second segment and are decidedly hooked. The 

 extent to which the setae are hooked has been pointed out by 

 St.-Joseph to be reduced by preservation (24. p. 338), so that 

 this does not seem to be a very important point. 



The opercular brood-pouch is somewhat cylindrical and bounded 

 proximally and distally by calcareous plates, the talon is red\xced 

 to a small quadrangular projection. 



The abdomen has eight segments, with large, more or less 

 sickle-shaped setae (fig. 9 b) and an asetigerovis anal segment. 



