194 MOLLUSCA. 
This species is remarkable for its broad, crescentic, and somewhat 
excavated columella, much as in the genus Lacuna. In this respect, 
and in the absence of an angle at the base of the axis, it differs chiefly 
from M. magellanica. Both of them have somewhat the aspect of 
Rotella. 
Figures 230, 230a, two views of the shell; 2304, outline of the 
aperture, enlarged. 
Marcarira conica (D’Orsieny), Voy. dans l’Amer. Merid. 
ANIMAL quite colourless, and remarkable for the great length of its 
tentacles and lateral filaments, of which there are four on each side. 
Eyes very large and black, situated near the base of the tentacles, 
without any perceptible pedicle or enlargement. Foot long and nar- 
row, obtuse posteriorly, truncate anteriorly, with no prolongation of 
the angles. 
Brought up on the cable at Scapenham Bay, Patagonia. [1. p. c.] 
Figure 229, the animal, with the shell, as in motion, magnified , 
229 a, 229, enlarged view of the head, above and below; 229, natu- 
ral size. 
Lacuna carinaTA (Gould). 
Testa parva, tenuis, ovato-globosa, epidermide corneo undulatim tenut- 
striato induta: spira anfractibus quinque ventricosis, ultimo carina 
filosa cincto: apertura semicircularis, dimidiam teste adequans ; 
columella rotundata. 
Lacuna carinata, Goutp ; Proceed. Boston Soc. Nat. Hist., ui. 75. 
November 1848. Expedition Shells, 52. 
The ANIMAL is much as in Littorina, with two filaments on the 
foot behind the operculum. Its motions were tolerably active; it 
crawled in an inverted position at the surface of the water, and when 
driven down, it hung by a thread of mucus, by means of which it 
