400 SPIRORBIS GRANULATUS. 
The tube is dextral, turning from first coil from left to right, somewhat flattened on 
stones, and with three ridges in the fully developed forms. The last whorl is large, and a 
process projects in some on the outer border. The central umbilicus is distinct with the 
apex in the pit. On the whole, the tube is more regularly coiled than that of S. granulatus, 
which often presents considerable irregularity in its coils and occasionally is flattened, this 
especially affecting the central umbilicus, these changes beng emphasised in the older 
examples. Moreover, in the Northern form, the three ridges are more boldly marked 
and the grooves deeper, whilst there is a tendency to projections of the terminations of 
the ridges around the circular aperture of the thicker tube. — 
The collar-bristles of S. Pagenstecheri quite differ from those of S. granulatus, being devoid 
of a gap, and the serrations are so minute on the tapering portion of the blade as to be indis- 
tinguishable, whilst at the broad web at the base distinct though fine serrations pass from 
the edge obliquely downward and backward (in regard to the anterior edge) over the web. 
Only three pairs of bristles seem to be present—the collar and two others and in the third 
tuft a sickle-shaped bristle occurred. Caullery and Mesnil give a good figure, but the 
lithographic ink obscures certain of the finer characters, such as the very slight concavity 
beyond the spinous basal web of the tip. A figure (Plate CXXXVII, fig. 23) is given for 
comparison, especially as the species may yet be met with on our southern shores. It is 
common at Naples on stones and Zostera. 
Langerhans! (1880) describes the tubes on algze as showing all the coils, which are marked 
by transverse lines, whereas those on stones are less regular and with a smaller aperture. 
The anterior region is reddish, the glandular coating of the intestine dark violet and the eges 
ed. He figures the collar-bristle with a differential web, but no distinct gap, whilst the 
sickle-shaped form from the third tuft 1s serrated distally with a slight wing inferiorly. He 
found ova in the first four abdominal segments and sperms posteriorly. 
Miss Bush (1908) places this form under those in which the “ fin” of the collar-bristle 
is defined only by a more or less definite notch, which “ entirely disappears,” forming simple 
tapered blades, which leave the shaft at an angle. This would not appear to be the rule 
in examples from Naples and Ireland. Her S. pusilloides is the Mera pusilla of De St. Joseph, 
but as Rathke used the specific name pusilla for a species from the Black Sea, she suggested 
the term mentioned. So far as can be seen, it would appear to be a young form of 
S. Pagenstecherv. 
b) 
Division II —Tube Sinstral. 
A. Incubation in Tube. 
6. SPIRORBIS GRANULATUS, Linnwus, 1767. Plate CXXII, figs. 7—7h—body, operculum, 
branchia, ova and larve; Plate CXXXII, figs. 5, 5’, 5’, 5a, 5c—bristles, 5d—tubes ; 
Plate CX XXIII, figs. 12 and 12a—operculum and branchie; Plate CXX XVII, fig. 22— 
collar-bristle ; Plate CX XXVIII, figs. 15 and 15a—hooks. 
Specific Characters—Cephalic collar split dorsally, but entire ventrally. Branchie pale, 
or with a tinge of red, especially at the base of the filaments, ten in number ; filaments taper 
' “Zeitschr. f. wiss. Zool.” Bd. xxxiv, p. 123, Taf. iv, fig. 42. 
