120 
MOLLUSCA. 
[Sessilia. 
Found on the Northumberland coast, near Seaton. In Lady 
Jardine’s cabinet. 
5. Pentelasmis radula, pi. LI, f. 3. 
Anatifa radula, First Ed., pi. 5, f. 3 ; Pentelasmis radula, 
Leach, MSS.; Lepas dentata. Brown, Ency. Brit., VI, p. 404. 
Shell subcompressed ; the larger valves acutely pointed, with 
regular series of prominent, oblique ribs, their anterior edges 
with six sharp, saw-like teeth, the superior ones largest, and 
gradually diminishing as they descend, thickly beset with sharp, 
imbricated scales, which have a rasp-like appearance ; superior 
valves terminating in a lengthened, acute point, and covered by 
undulating, rough striae ; dorsal valve arcuated, and smooth ; 
peduncle very small. 
Besides the ribs on the larger valves, the series of teeth on 
the anterior margins of the larger valves will at once distinguish 
this curious species from P. dentatus, in which the serrated 
teeth are placed on the centre of the dorsal valve. 
Found on the Devonshire coast, but is very rare. 
6. Pentelasmis fasciculaeia, pi. LI, f. 2. 
Anatifa fascicularia. First Ed., pi. 5, f. 2 ; Pentalasmis 
Ellisii, Leach, MSS., p. 1 ; Anatifa vitrea, Lamarck, V, p. 
405; Ellis, Zoophytes, p. 167> ph L5, f. 6; Lepas fascicularis, 
Montagu, p. 557 ; Maton and Rackett, p. 30 ; Lepas dilata, 
Donovan, pi. 144. 
Shell of a pale horn-colour, extremely thin and fragile; valves 
with large wrinkles; larger valves much expanded posteriorly, 
and becoming suddenly hollow, terminate in a beak-like point ; 
dorsal valve with an acute protuberance in its centre, and fre- 
quently with one below ; apicial valves much pointed, and have 
a considerable inclination backwards, producing a convexity on 
the anterior side of the shell ; peduncle very short, and very 
thin. 
This species is always found congregating in large masses. 
First found in the British Channel, and has been since met 
with on many of the British coasts, and especially on the west- 
ern coast of Ireland. 
ORDER II.— SESSILIA. 
Genus 1. — Pyugoma. — S avigny. 
Shell univalve, somewhat conical, generally compressed, and 
usually seated on Madrepores or other zoophytes ; open at the 
apex, which is small, and protected by a four-valved operculum, 
the posterior ones sometimes much elongated, these are varia- 
ble, and closed at the base by a deeply cup-shaped testaceous 
valve ; inside perpendicularly striated or grooved. 
1. Pyrgoma Anglica, pi. LIII, f. 27, 28, 29- 
Adna Anglica, First Ed., pi. 7> f* 27j 28, 29 ; Leach, MSS., 
p. 1. 
Shell conical, longitudinally ribbed, with many, nearly obso- 
lete, transverse wrinkles ; apex with a very small aperture, and 
protected by a bivalve, obliquely striated operculum; colour 
rosy. • 
Fig. 28, the operculum. 
Inhabits the CoryopTiillia Anglica, and is frequently found 
in Plymouth Sound. 
Genus 2. — Balanus — Bruguiere. 
Shell sessile, conical ; frequently an elongated cone ; com- 
posed of six valves, four of which are larger than the others, 
and of nearly equal size, and all of them locked by their 
sides ; apex open, of a subtrigonal or elliptical form ; base 
closed by a testaceous plate, by which it adheres to extra- 
neous substances ; operculum bipartite, and consisting of four 
valves, of which the posterior pair are the most prominent; 
exterior surface always covered by a thin, elastic, horny epi- 
dermis. 
1. Balanus balanoides, pi. LIII, f. 17, and pi. LIV, f. 
4, 5. 
Balanus ovularis. First Ed., pi. 6, f. 4, 5, and pi. 7, f. 17 ; 
Lamarck, V, p. 392; Balanus balanoides, Montagu, p. 7 ; Lepas 
balanoides, Donovan, pi. 36, f. 2 ; Maton and Rackett, p. 23 ; 
Brown, Ency. Brit., VI, p. 402. 
Shell subconic, subdepressed; valves smooth, white, some- 
times deeply sulcated at the base ; aperture wide ; operculum 
with the two anterior valves slightly striated transversely, the 
posterior ones smooth. 
Fig. 8, 9> valves of the operculum. 
Fig. 5, an elongated variety. 
A very common species, adhering to muscles and oysters. 
2. Balanus communis, pi. LIII, f. 23, and pi. LIV, f. 1. 
Balanus communis. First Ed., pi. 6, f. 1, and pi. 7, f. 23; 
Montagu, p. 6 ; Lepas Balanus, Pennant, IV, p. 72, pi. 37, f. 
4 ; Donovan, I, pi. 30, f. 1 ; Maton and Rackett, p. 23 ; Fle- 
ming, Edin. Ency., Art. Conch., p. 102. 
Shell strong, rugged, conic, compartments unequal, with 
many irregular, longitudinal, squammose ribs ; the interstices 
with transverse wrinkles ; aperture rather contracted, and fur- 
nished with a four-valved operculum ; posterior valves spreading 
a little at the apex ; anterior valves transversely striated, and 
provided with a longitudinal furrow ; colour cinereous-brown. 
Common on most of the coasts of Britain and Ireland, ad- 
hering to extraneous substances. 
3. Balanus rugosus, pi; LIII, f. 4, 7> 8, and 21, and pi. 
LIV, f. 6. 
Balanus rugosus. First Ed., pi. 6, f. 6, and pi. 7, f. 4 and 20 ; 
Montagu, p. 8; Fleming, Edin. Ency., Art. Conch., p. 101; 
Maton and Rackett, p. 25; Lepas borealis, Donovan, pi. 160, 
lower figure. 
Shell subconic, divided into six compartments by irregular, 
inequidistant furrows, those of the posterior side broadest, and 
crossed with deep divisions, formed by the lines of growth, 
these are sometimes wrinkled or striated longitudinally ; aper- 
ture very large, inner margin transversely ridged, and closed 
by a four-valved operculum ; the dorsal valves a little apart and 
reflexed at the apex; upper half of anterior valves smooth, 
with transverse, strong striae on their lower half; colour cream- 
white. 
Fig. 21, an elongated variety, the B. fistulosus of authors. 
Fig. 13, 14, the operculum. 
Common on many of the British and Irish coasts. 
4. Balanus costatus, pi. LIV, f. 2, 3. 
Balanus costatus. First Ed., pi. 6, f. 2, 3 ; Montagu, p. 1 1 ; 
Fleming, Edin. Ency., Art. Conch., p. 101 ; Lepas costata, 
Donovan, I, pi. 30, f. 2 ; Maton and Rackett, p. 24. 
