384 SPIRORBIS. 
Genus CLXXXIV.—Sprrorsis, Daudin, 1800. 
SYNONYMS. 
1759. Coretus, Baster. Naturk. Uitspan., p.48. 1774. Dinotus, Guettard. Mém., p. 133 (tab. 
Ixxi, figs. 1,2). 1800. Spirorbis, Daudin. Rec,p.37. 1803. Serpula, Linn., Miller, Montagu, Grube, 
Turton, etc. 1808. Charybs, Montfiore. Conch. Syst.,i, p. 107. 1810. Anatomus, idem. Ibid., ii, 
p- 279. 1815. Spirillum, Oken. N.G.,i,p.381. 1815. Spirorbis, Leach. Encycl. Brit. Suppl., i, 
p. 452. 1818. Spirorbis, Lamarck. Anim. s. Vert., vol. v, p. 358. 1820. Spirorbis, Schweigger. 
Handbuch der Naturg., p.60i. 1822. Spirorbis, Fleming. Philos. Zool.,p.602. 1825. Heterodisca, 
idem. Edinb. Philos. Journ., p. 247. 1829. Spirillum, Hichwald. Zool. Spec., i, p. 257. 1830. 
Spirorbis, Fleming. Edinb. Encyclop., vi, p. 68. 1833-41. Coretus,Oken. Allgem. N. G., v, p. 557. 
1845. Spirorbis, Johnston. Ann. Nat. Hist.,xvi,p.450. 1851. Spirorbis,Grube. Fam. der Annel., 
pp. 92 and 143. 
Cephalic collar split dorsally, but continuous ventrally as in Filograna. Branchiz few, 
four to five, on each side ; filaments with terminal processes and a series of pinnules. Oper- 
culum spatulate or clavate ; in some it acts as a brood-pouch; always the second on the concave 
side (the right in dextral and the left in sinistral, Pixell). Body typical, ending in an anus 
with two papille. Anterior region of three or four bristled segments and two rows of hooks. 
Mouth in the centre, with a short palp on each side. Between the anterior and posterior 
regions is an asetigerous part. Posterior region with eight to forty segments. Thoracic 
excretory organs unite in the middle line, and have a single duct. Abdominal nephridia 
simple tubes. Bristles of the first series (collar) are distinctive and differ from second and 
third, which also have hooks, and occasionally the bristles of the third diverge. Ventral 
bristles of posterior region geniculate. Anterior and posterior hooks avicular, with a long 
serrated anterior edge and a modified main fang inferiorly (Pixell). The posterior hooks 
are smaller. Hermaphrodite. Tube calcareous, coiled, dextral in some, sinistral in others. 
The genus is cosmopolitan in distribution. 
The genus Spirorbis was established by Daudin’ for the forms with flatly rolled shells 
after the manner of Planorbis, but Savigny did not follow him. 
The earlier British zoologists, as a rule, paid little attention to the Spirorbids, but Adams 
and Montagu considerably augmented our knowledge of native species. Writers on Mollusca 
often alluded to and figured their tubes. 
Philippi (1844) gives the characters as :—Operculum calcareous, obliquely truncated ; 
shell small, always spirally wound, branchize of few filaments. At the same date Thorpe, 
in his ‘ Marine Conchology,’ figured a few, e.g., Fig. 1054 (fig. 30), on a piece of stone. 
Morch (1861—1863), in his ‘ Revisio Critica Serpulidarum,’ has twenty-seven species of 
Spirorbids which he distinguishes by their tubes. 
Spirorbis was omitted from its place amongst the Serpulids in Dr. Johnston’s ‘Cata- 
logue of Worms in the British Museum’ (1865), probably from failing health, for he was 
acquainted with most of the species. Dr. Baird inserted an account of the British forms 
in the Appendix. As many had been described only from the shelly tubes considerable 
changes are now necessary. 
1 «Molluse. vers. Zooph., Paris, 1800. 
