MESSRS. HANCOCK AND EMBLETON ON THE ANATOMY OF DORIS. 213 
It is small in proportion, and in general form has resemblance to that of D. tubercu^ 
lata ; but in addition there is the singular appendage of a lentil-shaped organ, having 
all the characters of a gizzard*. This is attached by a short tubular pedicle to the 
upper part of the buccal mass, a little in front of the oesophagus. This buccal giz- 
zard is not much inferior in size to the buccal mass itself : its walls are thick, its 
external surface on each side presents numerous muscular bundles radiating from a 
centre, and its peripheral margin is bounded by a strong belt of muscle. Its inner 
surface is smooth, but tough, and its cavity communicates with the mouth through 
the pedicle, which is itself muscular. There is nothing to discredit the idea that 
we have here an organ added to the buccal mass for the more perfect trituration of 
the food, and which may probably at the same time act in promoting deglutition, for 
there is along the roof of the mouth apparently a groove leading from the pedicle in 
the direction of the oesophagus. 
In this species there is a modification of the tongue : it is here long and narrow ; there 
are twenty-six or twenty-eight rows of toothlets, two only in each row ; one toothlet 
is placed on each side of the median line. AbouT eleven rows are engaged in prehen- 
sion. The tocithlets are long, stout, arched spines. There is likewise in this species 
a prehensile collar, which, instead of being denticulated, is roughened with transverse 
irregular rows of short minute papillae. Moreover, there exists a minute pair of rudi- 
mentary jaws; but as both these parts exist also in D. pilosa, the description given 
under that head may sufiice for D. bilamellata also. 
D. aspera\ and D. depressa have likewise the narrow tongue and buccal gizzard. 
In D. pilosa the buccal mass:}: differs a good deal from the above forms. It is 
large, and the channel of the mouth opens into its under surface instead of in front, 
as in the other species. The difference of form is owing mainly to the apparent in- 
corporation of a gizzard-like organ with the anterior part of the buccal mass. That 
organ has the radiating muscular fibres, and the peripheral belt observable in the 
gizzard of D. bilamellata. It is placed immediately in front of the oesophagus, and 
its connexion with deglutition is more evident. The tongue § is of the same type tis 
that of Z). bilamellata, but the teeth have their margins denticulated. 
The prehensile collar || is present, and is different in form from that of D. repanda. 
It is divided into two lateral halves ; its spines, which are directed inwards, are very 
densely crowded, being for the most part like bifid stumps. The two parts of the 
collar are broad below, where they are somewhat separated, and taper to fine points 
above. We have here, in addition to the prehensile collar, a pair of minute rudi- 
mentary triangular horny plates or jaws^, which are situated between and imme- 
diately behind the lower separated ends of the collar. They are united in front for 
more than two-thirds of their length, and are imbedded in the lower part of the 
buccal lip, having only their free points exposed. Attached to the posterior border 
of each of these free parts of the plates is a thin transparent tough membrane, which 
* Plate XII. fig. 5. t Plate XII. fig. 14. % Plate XII. fig. 4. 
§ Plate XII. figs. 6 and 7, |1 Plate XIII. figs. 7, 8, 9 , 10 and 11. ^ Plate XIII. fig. 12. 
