792 MISS HELEN PIXELL OK 



defini von Marenzeller." St.-Joseph also gives as another 

 characteristic of his genus Hyalopomatopsis, the presence of 

 capiUary setse in all the abdominal segments. 



Genus Spirorbis Daudin (6), 1800. 

 (Pis. LXXXYIII., LXXXIX. figs. 7-16.) 



Genei'ic characteristics and Schemes of classification : — 



1. Calcareous tubes coiled in a dextral or sinistral spiral. 



The method of coiling and the markings on the tube have 

 been used by Bush (3) in drawing up Table I., but the 

 coiling of the tubes is variable {cf. figs. 8 a and h), being 

 determined to a great extent by the nature of the sub- 

 stratum, and as Caulleiy & Mesnil (5) have already 

 pointed out there is no constancy in either coiling or 

 markings. 



2. Branchiae are constant in diflferent species, the operculum 



with terminal calcareous plate, alwaj^s occurring as the 

 second on the concave side {i. e. the right in dextral forms 

 and left in sinistral ; since the animal lies with its back 

 towards the substratum). 



3. Thoracic segments generally 3 — the first having only dorsal 



setfe — the two following have on each side an uncinigerous 

 torus as well. In the subgenera given the prefix Para- 

 by OauUery & Mesnil an extra torus (and in 8p. can- 

 cellatus a fascicle of dorsal setae also) is developed on 

 the concave side of the animal ; this condition has been 

 described in the following Table of Classification (p. 794) 

 as 3 1 setigerous segments. 



In -S^. amhilateralis, sp. n., there are four complete setigeroiis 

 segments, although the fourth on the convex side is very reduced. 

 This specimen therefore approaches the hypothetical Prospirorhis, 

 described by Caullery & Mesnil (5. p. 233), who point out 

 that the genus S2nrorbis has been evolved from other Serpulidse, 

 which have the characteristic greater number of thoiacic segments, 

 by a gradual reduction. I have therefore placed this species in a 

 new sub-genus Protolceospira. 



4. Abdominal segments 8-40. 



Between the thorax and the abdomen is a more or less long 

 asetigerous region — often crowded with ova. The spermatozoa 

 develop in the postei'ior setigerous segments. 



5. The thoracic setae are distinctive and the differences are of 



use as specific characteristics. Table II. given by Bush 

 (3. p. 261) is drawn up Avith regard to these and the 

 direction of the coiling alone. 



As a rule, the first thoracic segment has some slender capillary 

 setae forming the inferior part of the fascicle (fig. 14 6) — the 



