6 DR J. STEPHENSON ON 
head, just in front of the cephalic grooves and in their concavity, there is to be seen 
a circular area, rather indefinite in its limits, which is of a lighter brown than the 
surrounding parts; with an ordinary microscope nothing further is to be made out, 
but with a binocular it appears that this area is slightly depressed below the general 
surface (figs. 1, 2). It is apparently this area which corresponds to the oval outline 
in MacIntosu’s figure. 
Sections show that there is no cerebral organ of the usual type—that is, that there 
are no canals or sacs; the depressed areas just mentioned are, however, recognisable . 
as areas of the epidermis with cells and ciliation like those of the cephalic grooves ; 
the areas are sunk below the general surface, and, owing probably to contraction in 
killing and fixing, their margins are much better defined than in life and project 
inwards towards the centre of the area (fig. 3). 
The species, therefore, does not form an exception—at least not such a marked 
exception as would be inferred from previous descriptions—to the general rule for the 
genus in regard to the cerebral organs. 
A well-developed inner (splanchnic) circular muscular layer is characteristic of 
the family Tubulanide (Carinellidee) ; but this particular species is stated to form 
an exception to the rule. Thus BUrcErR (5) writes: “Die innere Ringmuskelschicht 
ist ziemlich schwach entwickelt, nur das dorsale muskelfaserkreuz ist vorhanden.” 
My specimens must differ markedly from those on which this statement is founded ; 
they agree with others of the family in having a well-developed inner circular 
layer, while, on the other hand, the dorsal crossing of the fibres (as represented, e.g., 
for Tubulanus superbus, 5, p. 3, fig. 1; 1, p. 169, fig. viii.) is not recognisable. 
A feature, the description of which I have not met with elsewhere, is the character of 
the epithelial lining in the most anterior part of the proboscis. Almost immediately 
behind the spot where the proboscis becomes free within its sheath the lining epithe- 
lium of its dorsal, and somewhat less markedly of its ventral, wall is formed by a compact 
mass of tall and very narrow cells. This patch, elongated transversely to a semicircle 
which comprises the dorsal half of the circumference of the proboscis, is narrow antero- 
posteriorly, so that in a longitudinal section it appears as a cushion-like or fan-like 
projection (figs. 4, 5). The cells of which it is composed stain deeply, and are of a very 
different appearance from the much lighter, more loosely arranged, and more ragged- 
looking cells which succeed them; two layers of nuclei are visible, one near the base, 
the other at about the middle of the ‘cushion.’ The appearances are similar, but the 
cells are not so high, on the ventral wall of the tube (fig. 4). 
Cephalothrix linearis (J. Rathke). 
Under the name Cephalothrix linearis, MacInrosH has united certain forms which 
other writers have separated under the names C. linearis and C. rufifrons (or bioculata). 
It is 4 question how far the Millport specimens bear out this separation. 
