i) 
oS 
7 
DENTALIUM. 
D. entaris, Linn. et Auct. 
D. entalis, Brit. Moll. ii. p. 449, pl. 57. f. 11. 
I have only seen one live specimen of the D. entalis; the 
organs have the same characters as those of the Tarentinum, 
but it is very distinct; the colour is snow-white, and on 
comparison of two shells of the same size, the D. entahs will 
be found much more slender; the branchiz are of a paler 
green, more scanty, thin and delicate. 
Having had good opportunities of reviewing my notes, I 
have thought that it would be desirable to mention the result ; 
and I am the more anxious to do so, as I have the misfortune 
to differ on all essentials with zoologists whose talents have 
long stamped their judgment on these subjects as authorities 
scarcely to be disputed. I am unable to make any material 
correction in the preceding observations ; I can only add some 
fresh incidents and offer a few explanations. In carrying out 
these views I must again allude to M. Deshayes’ and his 
coadjutor M. d’Orbigny’s monograph ; it appears to me that 
there are in it some misconceptions, in addition to those I have 
already pointed out, which if passed over may mislead. 
M. Deshayes says that the convexity of the shell answers to 
the dorsal range, and the concavity to the ventral ; the reverse 
is the case, as I have proved in a hundred specimens, unless it 
be contended that the foot is placed above the head or buccal 
pouch on the dorsal range, stead of being under it on the 
ventral line, agreeably to the order of nature. Again, the 
heart is stated to be fixed on the dorsal surface above the 
stomach, and in the figure delineated it is lymg on that organ 
and exceeding it in length; but repeated examiations inform 
me that what is called and figured as the heart is the masti- 
catory apparatus and intestine, which le in the stomachal 
cavity, and demonstrate their presence by a marked inflation. 
The heart, as I have mentioned, is a minute organ at the 
base, but separated from the stomach by a septum or rib, 
and immersed in the centre of the dorsal and ventral surfaces ; 
