SPIRORBIS SPIRILLUM. 391 
stone. They are thick, translucent, with three longitudinal ribs, and prolonged into teeth 
at the aperture. They are vitreous, translucent, or have the aspect of chaleedony—which 
accounts for the title, ““ Kalkedonagtigt ”’ of Levinsen, only their nature is calcareous and 
not siliceous. Internally is a violet membrane, whence their specific name, which makes the 
tube double. 
Sterzinger (1909), after Caullery and Mesnil, figures the operculum as concentrically 
ringed and the first bristles as devoid of a gap. 
b. Tube opaque; three thoracic segments. 
2. SPIRORBIS SPIRILLUM, Janneus, 1760. Plate CXXII, figs. 9—9b—opercula and 
branchia; Plate CXXXII, figs. 6—6b—bristles, 6c —6d—tubes, 6e—operculum, 
6f—hook. 
Specific Characters—Collar normal. Branchie four on each side, and the terminal 
processes of the filaments are short (in the preparations) so that they do not project beyond 
the pinne, which also are short. Operculum a shallow vase with a foot or process (talon), 
the lower edge of which is crenate. No brood-pouch. Body typical. Upwards of twenty 
segments, three anterior segments with bristles; abdominal segments eighteen to twenty. 
Two papille at the anus. Collar-bristles have no gap at the base of the terminal blade. 
They have long, straight shafts, dilated at the shoulder, and the terminal blade is sharply 
bent backward, tapered and coarsely serrated. Hooks somewhat triangular in outline, 
the apex being superior. Anterior edge finely serrated and the main fang not conspicuous. 
Tube dextral, quite smooth, more or less translucent, the aperture in some being raised so as 
to give a lax aspect to the spire. It is flattened on the attached surface. 
This species has a dextral tube, and falls under Caullery and Mesnil’s Dexiospira with 
three thoracic segments. Incubation is carried on in the tube. The first bristles have no 
basal notch or fin. Posterior region with ten to twenty setigerous segments. 
SYNONYMS. 
1739. Serpula spirillum, Plancus. Conch., ‘l'ab. i, fig. 8. 
1747. aA spirorbis, Linneeus. Westgotha Resa, p. 198. 
We _ cochleze, Baster. Philos. Trans., vol. 1, p. 277, Tab. vii, fig. 6 0. 
1758. 35 spirillum, Linneeus. Syst. Nat., ed. x, p. 786. 
fe »  sptrorbis,idem. Ihbid., p. 787. 
1761. _ sptrillum, idem. Fauna Suecica, p. 535. 
1762. Coretus Eschara minima millepora crustaceex cellulis twbifornuis, Baster. Natuurkun. Uitspann., 
vol. i, p. 48, Tab. u, fig. 5 0. 
1767. Serpula spirillwm, Linneus. Syst. Nat., ed. xu, p. 1264. 
mn 5 spirorbis, idem. Ibid., ed. xu, p. 1265. 
1769. Tubulus minimus levis, etc., Martini. Conch., vol. i, pp. 25, 59, Tab. i, figs. 21 a, b, c. 
1776. Serpula spirillum, O. F. Miller. Zool. Dan. Prod., p. 236, No. 2854. 
1780. 5 x Fabricius. Fauna Greenland, p. 376. 
- »  porrecta,idem. Ibid., p. 378. 
1784. 5 spirillum, Walker. Test. Minuta, figs. 13 and 14, 
1788. $0 5 Pallas. Nova Acta Acad. Petrop., t. 1, p. 286, Tab. v, fig. 21. 
