418 SPIRORBIS MILITARIS. 
of teeth, about twenty in number, along the anterior edge, and these stand out prominently, 
sloping downward and outward. The main fang or terminal process is comparatively small, 
and it does not show the bifid condition distinctly. A slight bay occurs behind it. The 
posterior hooks are much smaller, but have a similar outline. 
Reproduction.—The species is hermaphrodite, the ova occurring anteriorly and the sperms 
posteriorly. Those procured in Guernsey and Herm in July and August had large ova and 
embryos in the opercular brood-pouch. Lo Bianco found the same in June and July at 
Naples. Several stages of the larva of this form are shown by Claparede and Mecznikow! 
(1868), and they are parallel with those of their S. Pagenstecheri. The blunt cephalic lobe 
of the youngest stage has two eyes with lenses, and two without them, separate masses of 
orange yolk in the body, a prototroch, a tuft of cilia anteriorly and posteriorly, and an 
anterior or thoracic membrane. The subsequent stages show a double process on the snout, 
and the characteristic bristles of the anterior region. 
Claparéde (1868) gave an account of this form with figures of the operculum and bristles 
from Neapolitan examples, placing it under a new genus, Peleolaria, but, as has already 
been shown, it falls naturally under the old genus Spirorbis. He recognised its 
hermaphrodite condition, as well as found the larvee at various stages inside the helmet- 
like operculum. 
Salensky? studied the development of Sp. militaris to the period of fixation and the 
formation of the operculum, which at first 1s concave instead of convex, and, as Caullery 
and Mesnil state, thus falls mto lne with the usual condition of the operculum in the 
group. 
The exact relationship of this form with Spzrorbis cornu-arietis (Philippi) of Marion 
and Bobretzky, and as mentioned by Caullery and Mesnil, is still uncertain, for the latter 
authors state that in the absence of the operculum it is impossible to distinguish the one 
from the other. It is therefore a question if the operculum alone be relied on. Caullery 
and Mesnil unite the Sp. granulatus of Langerhans with this form. 
Trene Sterzinger® (1909), in a careful and excellently illustrated account of a collection 
from Suez, describes a variety of this species with smaller processes on the summit of the 
operculum. The gap at the base of the tip of the collar-bristles is marked. 
Two forms, familiar in the literature of the subject, are not entered here, viz., Spirorbis 
heierostrophus, Montagu, and Sprrorbis carinatus, Montagu, since both are probably included 
in the forms dealt with, and, at any rate, the uncertainty can only be removed by a careful 
re-examination of fresh animals. Miss Bush and others do not seem to have formed a 
definite opinion about either. The first is Sprrorbis heterostrophus, Montagu, 1803. 
At first sight the dried tube resembles that of S. granulatus, but it is dextral, whereas 
that of the form mentioned is sinistral. The tube (Plate CX XXIII, fig. 5, from an English 
example) is coiled from left to right, and has a deep groove on the summit, and two ridges. 
1 «Zeitschr. f. wiss. Zool., Bd. xix, p. 200, Taf. xvi, figs. 3—3 nr. 
2 “Arch. Biol.,’ t. iv, p. 148, 1883. 
> “Sitzungsber. k. Akad. Wiss. Wien.,’ Bd. exvii, p. 1451, ete. 
