(_d._) Rostrum,
(_e._) Sub-rostrum, both viewed a little obliquely.
4. _Pollicipes spinosus_, one and a half nat. size.
5. _Pollicipes sertus_, one and a half nat. size.
TAB. VIII.
Fig.
1. A piece of rock bored in two directions by _Lithotrya dorsalis_, with the calcareous basal discs in the upper cavity, serving as a bridge for crossing an old cavity.
About twice natural size.
1_a'._ _Lithotrya dorsalis_, (nearly twice nat. size), with the basal calcareous cup adherent; (_a_), rostrum on same scale, seen externally.
1_b'._ _Lithotrya dorsalis_, rostrum and the rostral corners of the two scuta, together with a small portion of the subjacent membrane of the peduncle, with its calcareous scales; viewed externally, greatly magnified, showing the inferior crenated edges of the scales.
1_c'._ _Lithotrya dorsalis_, basal calcareous cup, one and a half the natural size; this is the largest specimen which I have seen.
2. _Lithotrya Nicobarica_, (magnified nearly twice;) attached to the rock, copied from Reinhardt; (_a_), rostrum on the same scale, with the other valves, seen externally; (_b_), section of the row of discs; (_c_), extreme point of the peduncle, extending beneath the row of discs.
2_a'._ Rock bored by _Lithotrya Nicobarica_, showing the row of calcareous discs, copied from Reinhardt.
3. _Lithotrya cauta_, magnified between seven and eight times; (_a_), scutum; (_b_), tergum.
3_c._ _Lithotrya cauta_, latus, greatly magnified.
3_d._ _Lithotrya cauta_, uppermost scales of the peduncle, greatly magnified.
3_e._ _Lithotrya cauta_, star-shaped discs of hard chitine, supported on a peduncle of the same substance, taken from the lower exterior surface of the peduncle, very greatly magnified.
4. _Lithotrya Rhodiopus_, (magnified five times,) internal views of; (_a_), scutum; (_b_), tergum; (_c_), latus; (_d_), carina.
5. _Lithotrya Valentiana_, (magnified between three and four times;) (_a_), internal view of scutum and tergum, locked together; (_b_), capitulum seen from vertically above; (_c_), internal view of carina; (_d_), section across the middle of the carina.
TAB. IX.
Fig.
1. _Lithotrya truncata_, (magnified four times.)
1_a'._ _Lithotrya truncata_, capitulum seen from vertically above, not so distinctly represented as in fig. 5 _b_, Pl. VIII.
1_b'._ _Lithotrya truncata_, internal views of valves; (_a_), rostrum, with a few subjacent scales of the peduncle; (_b_), scutum; (_c_), tergum; (_d_), carina.
2. A portion (about 1/10th of an inch square) of the surface of attachment of the peduncle of _Pollicipes polymerus_, seen from the outside, greatly magnified, showing the small circular (_bb_) patches of cement, poured out from the cement-ducts (_aa_) which lie within the peduncle.
2_a'._ A portion of a section, still more magnified, through the basal membrane of the peduncle, through one of the loops of the cement-ducts (_aa_), and through one of the circular patches (_b_) of cement.
3. Cement gland, duct, and ovarian tubes of _Conchoderma aurita_; (_aa_), ovarian tubes, with ova in process of formation; (_b_), cement-gland; (_c_), cement-duct.
4. _Conchoderma virgata_, enlarged, with one side of the capitulum and of the peduncle removed, to show the form and position of the body.
(_a._) tergum, edge of.
(_b._) mouth, with one of the palpi seen on the inner, upper corner.
(_c._) adductor scutorum muscle.
(_d._) orifice of acoustic (?) sack.
(_e._) scutum, occludent margin of.
(_f._) branching ovarian tubes within the peduncle.
(_g._) filamentary appendage on the prosoma.
(_h._) ditto, close to basal articulation of the first cirrus.
(_i._) ditto, on the pedicel of the first cirrus.
(_j._) ditto, on the pedicel of the third cirrus.
(_k._) ditto, on the pedicel of the fourth cirrus.
(_l._) ditto, on the pedicel of the fifth cirrus.
(_m._) edge of the carina.
(_n._) prosoma.
5. Apex of one of the filamentary appendages of _Conchoderma aurita_, greatly magnified, exhibiting the included branching testes.
6. Acoustic (?) sack of _Conchoderma virgata_, taken out of the acoustic meatus, with the diaphragm from the summit removed; greatly magnified.
7. Terminal part (magnified seven times), of the peduncle of an elongated specimen of _Scalpellum vulgare_, slit open, with the corium removed, showing the two cement-ducts (_aa_), and a row of circular patches (_bb_) of cement, by which the peduncle, along its rostral edge, is attached to the thin horny branches of the coralline. The larval antennae are seen at the terminal point, and the two cement-ducts can be traced into them.
TAB. X.
_Figures all greatly magnified._
Fig.
1. Mandibles of _Pollicipes mitella_: exhibiting the upper (_a_) and lower (_b_) articulations, and the three principal muscles; the short upper cut off muscle runs to its attachment at the base of the palpus.