184 PLEUROTOMID. 
scarcely any anterior canal; internal lip with a thick posterior 
callus; external lip thick within. P. pulchra, Gray (vii, 19). 
cLAvus, Montf. Tuberculated or spiny; aperture rather large ; 
internal lip smooth; outer lip produced below the sinus.  P. 
auriculifera, Lam. (lvii, 20). 
ANCISTROSYRINX, Dall. (Candelabrum, Dall.) Shell with the 
posterior surface of the whorls concave, with a broad deep sinus, 
bordered externally by a pectinated elevated frill, directed back- 
wards. P. eleyans, Dall. West Indies. 
BELA, Gray. Shell oval, fusiform, thin; spire produced ; canal 
short; sinus small, near the suture; columella flattened ; oper- 
culum pointed at both ends. Northern. P. turricula, Montf. 
(lvii, 21). 
BELOMITRA, Fischer, 1882. Shell like Bela, but with numerous 
plice on the columella. B. paradoxa, Fischer. Atlantic O., 627 
metres. 
LACHEsIS, Risso. (Annaand Nesea, Risso. Atoma, Bellardi?) 
Turriculated, with convex whorls and mammillated apex; lip- 
sinus obsolete ; operculum unguiform. Animal with converging 
tentacles, short siphon and short ovate foot. P. minima, Montf. 
(lvii, 22). 
CLAVATULA, Lam. (Clavicantha, Swainson. Mesochilostoma, 
Seely?) Subfusiform; spire produced ; whorls coronated ; aper- 
ture oval; canal short; columella smooth, sinuous; lip-sinus 
profound. P. imperialis, Lam. (Ivii, 23). 
CLIONELLA, Gray. Shell fusiform, longitudinally ribbed ; last 
whorl usually contracted in front; a more or less developed 
anterior canal; and posterior sinus. South Africa. A Melania- 
like shell, usually classed with Pirena, ete., and erroneously sup- 
posed to inhabit fresh waters. The eyes are placed near the tips 
of the tentacles, the foot is broad and very short. Operculum 
subelliptical with the nucleus near the middle of the inner side. 
Dentition, 1:11. P. bwecinoides, Lam, (lviii, 24). 
PERRONA, Schum., 1817. (Tomella, Swains.) Shell fusiform, 
subclaviform ; spire more or less elevated, smooth or carinated ; 
aperture somewhat narrow, terminating in a rather long canal ; 
inner lip callous near the suture. P, lineata, Lam. (lviii, 25). 
cLINURA, Bellardi. Ovately fusiform or turreted ; sinus deep, 
arcuate; lip greatly produced anteriorly, aliform; columella 
contorted; canal rather long, oblique. P. Calliope, Brocchi 
(Iviii, 27). 
CLATHURELLA,Carp. (Defrancia, Millet. Homostoma, Bellardi. ) 
Fusiform or turriculated; columellar lip without callosity except 
a small posterior tooth. No operculum. The cancellated surface, 
more ventricose form and more evident canal distinguish it 
from Mangelia, the emargination of the outer lip from Clavatula, 
