792 MISS HELEN PIXELL OX 



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

 characteristic of his genus Hycdopomatopsis, the presence of 

 capillary setfe in all the abdominal segments. 



Genus Spirorbis Daudin (6), 1800. 

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



Generic 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 b), being- 

 determined to a great extent by the natm-e of the sub- 

 stratum, and as Caullery & Mesnil (6) have already 

 pointed out there is no constancy in either coiling or 

 markings. 



2. Branchiae are constant in difi'erent 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 substi-atum). 



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



setae — the two following have on each side an uncinigerous 

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

 by Caullery & Mesnil an extra torus (and in S})- can- 

 cellat'us a fascicle of dorsal setse 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| setigerous segments. 



In S'})- ambilateralis, sp. n., there are four complete setigerous 

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

 This specimen therefore approaches the hypothetical Prosjnrorhis, 

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

 that the genus Spirorbis has been evolved from other Serpulidoe, 

 which have the characteristic greater number of thoiacic segments, 

 by a gradual i-eduction. I have therefore placed this species in a 

 new sub-genus Froiolceospira. 



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 sette are distinctive and the differences ai'e of 



use as specific characteristics. Table II. given by Bush 

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

 direction of the coiling alone. 



As a rule, the first thoracic segment hns some slender capillaiv 

 (seta^ forming the inferior part of the fascicle (fig. 14 b) — the 



