2 
mark. I have also obtained it attached to the heard of the 
greater Pinna, from the depth of above 40 fathoms ; but 
I have not, obtained the animal. 
D. DENTALIS. Turt. Lin. D. Striatum. Mont. Test. Brit, 
vol. 2, p. 495. Striated Tooth Shell. Rare, found by, 
Montagu at Falmouth; and by mjself attached to the 
Bvssus of a Pinna. 
D. GADUS. Mont. Test. Brit., vol. 2, p. 496, pi. 14, fig. 7- 
Montagu sajs it occurs at a distance from land, attached 
to the sounding lead of ships in the Channel. On this 
account I have ventured to class it with Cornish Shells. 
It has been supposed that the habit of this genus is to 
remain fixed in the sand or ooze, and there to protrude their 
organs for the purpose of laying hold on whatever food may 
chance to come near ; retreating into the shell on the 
approach of danger, after the manner of the Terebellae and 
Serpulee. But the observations of Mr. Lansdowne Guilding 
on a species which he examined in the West Indies, tend 
to overturn this opinion, and to displace the animal from its 
situation in the present classification. Placed in a vessel of 
water, observes this Gentleman, it drew itself along on its 
side; but this may have been owing to the shallow layer of 
sand in which it endeavoured to bury itself in the soup plate 
which contained it, where it might not have been able to 
assume its proper attitude. The creature moves tolerably 
quick, by sudden interrupted steps. When disturbed it 
retreats quickly into its shell, which has no operculum, as 
the Scrpulidae. After a time the cloak is protruded, the 
tentacula set in motion, and the vermiform active foot par- 
tially thrust out to explore its path. When it wishes to 
proceed apace, the foot with its petal-shaped alao closed 
round the stem, is protruded to its full length ; the aim are 
then suddenly expanded, and the base of the foot being 
forcibly contracted, the shell is brought forward, while those 
expansions laid open in the sand, prevent the apex of the 
foot from losing its advanced position. Of the place of the 
Dentalium in the natural system, continues Mr. Guilding' 
I will not venture to speak at this moment, though perhaps 
we shall not do wrong, iu the present state of our knowledge 
of the Molluscs, in placing it near the great family, or 1 
should rather say, great tribe of Linnean Patellae.” In i* s 
anal opening it resembles the genus Fissurella, while tb® 
opicial figure represents the posterior marginal rima °* 
Emarginula. Trans. Lin. Soc. vol. 17, p. 31. 
A MP BITRITEA . 
The tube membranous or horny, more or less studded will* 
sand or fragments of Shells. 
