POMATOCERUS TRIQUETER. 369 
Delle Chiaje, and he kindly furnishes two diagrams to illustrate the state of the parts, one, 
Fig. 169, giving an outline in vertical section, and the other, Fig. 170, showing a sagittal 
(horizontal) section. Such an arrangement conserves the secretion, whilst it does not diminish 
the strength of the tube. 
Fig. 168. Fra. 169. 
Fig. 168.—Diagram of a diaphragm secreted by Pomatocerus triqueter. After Arnold Watson. 
Fig, 169.—Diacrammatic vertical section of a camerated tube of P. triqueter. After Arnold Watson. 
In Montagu’s MS. volume (1808) in the Linnean Society is a drawing of “ Infundibula 
bicirrata,’ a Serpulid with three ridges and two grooves along the slightly bent, not 
coiled, calcareous tube, and a blunt operculum is present. It is difficult to be certain 
as to the species, but it has the appearance of Pomatocerus. 
Philippi (1844) made two species of this form, viz., P. tricuspis and Vermilva triquetra, 
the latter having an operculum with two appendages, and supporting a forked process with 
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Fie. 170.—Diagram of the camerated tube of P. triqueter in horizontal section. After Arnold Watson. 
obtuse ends. It is possible that Cuvier referred to this species as S. vermicularis, since he 
states that the operculum is armed with two or three points. 
De Quatrefages! (1850) gave a description of the nervous system of this species, which 
on the whole resembles that of Hydroides norvegica. The cephalic ganglia have smaller 
branchial trunks. 
Dr. Johnston’s Serpula Berkelyi (or S. Berkelew), from Berwick Bay, is represented by a 
tube with a dorsal keel in the British Museum, and the aperture seems to have been broken. 
A second collection has two specimens partially extracted from tubes attached to a board 
1 “Ann. Se. Nat.,’ 3° sér., t. xiv, p. 373. 
