TURRITELLA. 331 
Cecum trachea very active, but it is far surpassed by this 
animal; I put one of each in a watch-glass of sea-water, and 
with a camel’s-hair brush gave them a fair start, but the little 
one beat its competitor hollow, and accomplished a space of 
2 inches in 55 seconds; thus affording a proof, even in the 
Mollusca, that nature compensates for the small volume of 
the minute beings in giving them greater energy, vivacity and 
quickness. This creature I found by admeasurement to be 
z\jth of an inch long, and 35th of an inch in diameter. 
I have been thus particular, as it can fall to the lot of very 
few malacologists to see this curious species alive. 
TURRITELLA, Lamarck. 
T. communis, Risso et Auct. 
T. communis, Brit. Moll. iii. p. 172, pl. 89. f. 1,2, 3,5 (animal) pl. LI. 
f. 4. 
Turbo tenebra, Montagu. 
The incidents and peculiarities of this genus, of only one 
British species, in regard to its connection with the Holo- 
stomata and removal to this family, are so fully stated in the 
subjoied account of the comparison of Turritella with Ver- 
metus, as not to require further remark. 
Animal elongated, inhabitmg a brown, spirally ridged, 
turreted shell of 16-18 tapermg volutions. Mantle yellow, 
loose, ornamented at the upper part with a frmge of the same 
colour, of seven long and as many shorter strands, the longer 
ones being fimbriated at both edges, presenting a foliaceous 
aspect. In Vermetus, Philippi says, ‘mantle entire ;” but 
Sassi, “emarginate.’ The head is a small, flat, rounded 
muzzle, which always rests on the foot, yellow, with close-set, 
transverse, fine dark lines; in Vermetus the head is similar. 
Tentacula rather long, conical, pomted, tumid at the bases, 
yellow, with eyes at the external angles on only slight pro- 
minences; in Vermetus, teste Philippi, four tentacula, which 
however means, as regards two of them, eyes on swollen 
pedicles, as in Trochus. The foot is very short before and 
behind, scarcely extending to the first volution, yellow under- 
