> 3. POLYCERIDJS.
Shape generally limaciform with appendages. Teeth differentiated. Radnla often
narrow.
Genus i . Triopa J ohnston.
See Johnston, Miscellanea Zoologica, in Ann. Nat. Hist., 1838, p. 123; Bergh 20, pp. 12 16.
Limaciform; pallial margin and oral veil narrow but marked by a line of moderately
long papillge, smooth or tuberculate. Oral tentacles grooved. Rhinophores perfoliate
and retractile into short sheaths. Back usually tuberculate. Branchiae few (three), not
protected by special appendages. Penis armed with hooks. No jaws or labial armature.
Formula of radula about 13 +^{&j+ 1 . 0 . 1 + 1 + 13. First lateral slender, hamate;
second lateral larger and stouter with a double hook; remaining teeth flattish and
plate-like.
1. Tr. clavigera (0 . F. Muller).
(Pt. 4, Fam. 1, PI. 20.)
[Genus 2. Issa B ergh.
See Bergh 20, pp. 19—23.
This genus is hardly separable from Triopa in its external characters, and is distinguished
by having the marginal processes shorter and the dorsal processes longer, so
that the whole animal is sparsely studded with papillas. But the buccal parts are different.
There are two triangular jaws, and the formula of the radula is about 7 + 2 + 1 + 2 + 7.
The central tooth is a flat plate; the first and second laterals are both large and of a
clumsy hamate shape; the remaining teeth are flat plates.
1. I. lacera (Abildg.).
Body white; rhinophores and branchiee yellow.]
Genus 3. Crimora A. & H.
See Alder 1, pp. 73—74; Alder and Hancock 2, p. 263.
Limaciform; mantle indistinct, forming a veil with branched appendages over the
head and a pallial ridge which bears numerous filaments at the sides of the back. Oral
tentacles tubercular; rhinophores laminated and retractile within sheaths. Branchi®
three, tripinnate. The radula contains four or five kinds of teeth : (1) An imperfectly
hamate plate next to the rhachis«; (2) a large bicuspid tooth; (3) a few imperfectly
hamate plates which gradually become (4) more distinctly hamate; (5) very long, curved,
minutely serrulated, external teeth.
Some of the above characters may be merely specific, not generic. The original
descriptions say nothing about the genitalia or labial armature, but the latter is probably
absent.
1. Crimora papillata A. & H.
(Pt. 8, PI. II, figs. 1—5.)
Genus 4. Thecaeera F leming.
See Eliot, Journ. of Conchol., vol. ii, October, 1905, pp. 241—242.
Body limaciform. Oral veil indistinct, smooth or tuberculate. No pallial margin.
Rhinophores perfoliate, retractile into large sheaths. Branchiae three to seven, tripinnate,
with two lateral appendages. Penis armed with hooked spines (at any rate in Th. macu-
ligerd). Jaws with a wing-shaped process. Radula short with a formula of from
3 + 2 . 0 . 2 + 3 to 5 + 2 . 0 . 2 + 5. The two inner teeth are large and hamate; the
rest flat and plate-like.
1. Th. pennigera Montagu.
(Pt. 7, Fam. 1, PL. 21 a.)
2. Th. virescens A. & H.
3. Th. capitata A. & H.
Genus 5. Polycera Cuv.
See Bergh 19, pp. 3—27 ; Meyer and Mobius 1, pp. 49—56.
Body limaciform. Pallial margin not wide but marked by a tuberculate ridge at
the side and continuous round the head, where p f bears digitate processes or tubercles.
Branchiae simple, bi- or tripinnate, with one or more appendages on either side. Rhino-
phores perfoliate and contractile but without sheaths. Jaws with or without a wing-like
process. Radula with a formula varying from 4 + 2 . 0 . 2 + 4 to 8 + 2 . 0 . 2 + 8. The
two inner teeth are large and hamate; the others flattish. Penis armed with spines.
Prostate large.
Gray divided the genus into two: (a) Polycera sensu stricto, in which the
frontal margin is digitate, the dorsal appendages near the branchiae two only and large,
and the jaws have wing-like processes; (b) Palio, in which the frontal margin is tuberculate,
the appendages near the branchiae are small but several in number, and the jaws
have no wing-like process. These divisions may perhaps be kept as sections, but they
hardly amount to genera, and the differences are not so absolute as stated above. For
instance in Polycera quad/rilineata the branchial appendages are often palmate and subdivided
or even several in number, and separate; the frontal veil sometimes bears numerous
appendages of various sizes. (See, for example, Elmhirst, Annals Scottish Nat. Hist.,
1908, pp. 228—230.)