bet, Bd. i,
Tab. vi, fig. 9, 1790.

_P. capitulo, valvarum duobus aut pluribus sub-rostro verticillis
instructo: valvis albis, aut glaucis: pedunculo, squamarum densis
verticillis symmetrice dispositis._

Capitulum with two or more whorls of valves under the rostrum; valves
white or gray; scales on the peduncle symmetrically arranged in close
whorls.

Maxillae with three tufts of fine bristles, separated by larger spines:
segments in the first cirrus less than half the number of those in the
sixth cirrus: caudal appendages multi-articulate: filamentary appendages
attached to the prosoma.

Coast of Portugal; mouth of the Tagus. England,[64] Ireland, and
the Frith of Forth in Scotland. Mediterranean (according to
Brugiere): Teneriffe: Mogador, Africa.

[64] This species is said by Montagu ('Test. Brit. Supplement')
to have been found attached to drift timber in the Frith of
Forth, and to the bottom of a wrecked vessel towed into
Dartmouth. According to Mr. W. Thompson ('Annals of Nat. Hist.'
vol. xiii, p. 436), it has been found attached to wood-work near
Dublin.

Capitulum, obtusely triangular, massive: valves close together, rather
thick, with their exterior surfaces convex, naked, except in the lower
parts, where united together by tough, greenish-brown membrane,
destitute of spines. The edges of the orifice are widely bordered by
membrane, coloured fine crimson red. The valves, in a specimen with a
capitulum above three quarters of an inch long, were 52 in number; in a
specimen one fifth of an inch long, only between 20 and 30. Two whorls
of valves are distinct beneath the carina and rostrum. In one specimen
in Mr. Cuming's collection, with a capitulum 1.4 of an inch long, there
were three whorls beneath the rostrum, and four beneath the carina. The
scuta, terga, and carina are much larger than the other valves.

_Scuta_, oval, the basal and tergo-lateral margins sweeping into each
other, and the apex pointed; internally (Pl. VII, fig. 1 _a_) the pit
for the adductor muscle is deep.

_Terga_, larger than the scuta, internally (fig. 1 _a_) slightly
concave; carinal margin much curved and protuberant; basal angle blunt;
scutal margin either curved with the upper part straight, or formed of
two almost distinct lines, corresponding with the tergal margin of the
scutum, and with one of the sides of the upper latus.

_Carina_, much curved, extending far up between the terga,