y the calcareous basis,--by the manner in which the scuta and
terga are locked together,--by the two little fans of muscle attached to
near the basal points of the terga,--and perhaps by some of the
characters of the trophi; nevertheless, this affinity is far from being
well-marked, and I think is hardly so plain as in _Pollicipes mitella_.

1. LITHOTRYA DORSALIS. Pl. VIII, fig. 1 _a'_.

LITHOTRYA DORSALIS. _G.B. Sowerby._ Genera of Shells, April,
1822.

LEPAS DORSALIS. _Ellis._ Nat. Hist. Zoophytes, Tab. xv, fig. 5,
1786.

LITHOLEPAS DE MONT SERRAT. _De Blainville._ Dict. des Sc. Nat.,
Plate, fig. 5, 1824.

_L. scutis terga anguste obtegentibus: carina intus concava: rostro,
duorum aut trium squamarum subjacentium latitudinem aequante: lateribus,
squamarum quinque subjacentium longitudinem aequantibus, superficie
interna anguste elliptica: pedunculi squamis superioribus verticillum
secundum minus duplo superantibus._

Scuta, narrowly overlapping the terga: carina internally concave:
rostrum as wide as two or three of the subjacent scales: latera with
their internal surfaces narrowly elliptical, as long as five of the
subjacent scales: upper scales of the peduncle less than twice as large
as those in the second whorl.

Mandibles, with twice as many pectinations between the first and second
main teeth, as between the second and third teeth. Maxillae without a
notch, edge nearly straight, and spines very numerous: caudal appendages
exceeding, by half, the length of the pedicel of the sixth cirrus.

Barbadoes, West Indies; Venezuela; Honduras; imbedded in
limestone; Mus. Brit. Cuming and Stutchbury.

The state of preservation of the valves in different specimens varies
greatly; generally only two or three, or even only the last-formed
shelly layer, is preserved, the upper ones having scaled off; in a few
young specimens, however, all the layers were perfect. The carina is
generally better preserved than the other valves, and hence the upper
part usually projects freely; in one specimen no less than ten zones of
growth were preserved in the carina, whilst the other valves consisted
of only three: the terga generally project rather more than the scuta.
As each growth-layer is thick, if the scaling process had not taken
place, all the valves would have projected greatly. The little teeth lie
close together on the prominent serrated rims, on each zone of growth.
The internal s