196 PECTINIBRANCHIATA.—CERITHIADZ. 
an inch and a quarter in length, of a pale bay or 
drab hue, with prominent ribs, spotted with purple. 
The animal is blackish-grey speckled with white. 
The Wentletraps inhabit rather deep water, and 
affect a sandy or muddy bottom: hence they are 
obtained only by dredging. The species just de- 
scribed has been procured at various parts of our 
coast, but principally on the shores of Devonshire. 
FAMILY CERITHIADA. 
This group, as defined by our latest malacolo- 
gists, includes shells which at first sight appear to 
be very dissimilar, as the slender turreted Cerathium 
and the broad-lipped Pelican’s foot. ‘The genera 
are ‘remarkable for the muzzle-shaped heads and 
corresponding features of organization of the animals 
which construct them.” ‘They seem to constitute 
a group intermediate between those comb-gilled 
Gasteropoda which have entire mouths, and those 
which are furnished with siphons, partaking of and 
mingling many of the characters of both. 
GENUS APORRHAIS. 
A thick, massive, many-whorled shell marks 
this genus, subject to much alteration in form as it 
advances in age. In youth the aperture is simple, 
slightly angular, with a moderate canal; in adult 
age the canal becomes lengthened, and the outer 
margin of the shell is produced into a wide wing- 
like expansion, the edge of which projects in di- 
verging lobes or finger-like processes. 
The animal has a long muzzle; cylindrical ten- 
tacles, with the’ eyes placed on prominences at 
