ON ANNELIDA. 
83 
The anterior third of the body, a little broader than the rest, 
forms a sort of thoracic region, composed of seventeen segments : 
they are provided on each side with a pencil of seta?, above 
and underneath, with a sort of vertical cleft, with two lips, 
pretty similar in appearance to a long stigma, but which is really 
produced by the re-entrance of two very crowded ranks of setae, 
very short, and curved hook-wise. In the rest of the body, 
composed of more than one hundred and fifty segments, there 
are no other appendages but those ranks of hooked setae. 
The head of the terebella is but little distinct, and appears 
as it were truncated. We may nevertheless recognize there, 
by means of the appendages, several segments. The first, 
or labial, which advances more or less above the mouth, in 
the form of an epiglottis, and which supports at its upper 
face, a variable, but often a considerable number of cirrous 
barbies, of different lengths, and which are formed by a sort 
of shred, bending longitudinally underneath. The second 
ring constitutes the posterior lip ; it is much more narrow 
above than underneath. The third supports, on each side, a 
sort of membranaceous lobe, and forms a kind of neck. 
After the head, come the first three thoracic gills ; the gills 
are in the form of arbusculse, more or less ramified, and rather 
dorsal. The third pair is accompanied, underneath, with a 
pencil of simple seta?, but without any range of hooks. 
I he mouth very large, is anterior and inferior. 
The anus is terminal, folded, and circular. 
The organs of generation (or, to speak more properly the 
ovary), are terminated, according to Pallas, by a medial 
orifice, situated at the edge of the first segment of the abdo- 
minal band. 
In the organization of the terebella?, we may remark, as in 
all the chetopods, that the sub-gelatinous epidermis, is re- 
covered with the greatest facility, from the rest of the cuta- 
neous envelope. The dermis is confounded with the muscular 
