18 Mr. W. H. Dall on certain 
foot nearly orbicular, extremely thin and delicate, not high ; 
muzzle short, plain, without any strongly defined margination, 
with the end finely papillose and a little puckered; mouth 
small, furnished with two lateral pads covered with a cartila- 
ginous thin coat, which completely dissolves in liquor potasse, 
and hence can hardly be termed a jaw, though it occupies the 
place of the buccal plates in other genera; head moderate, not 
much produced, broader than long, extended laterally into a 
single, rather short and stout tentacle on each side; tentacles 
showing slight transverse ridges (due to contraction ?), desti- 
tute of any basal elbow or tubercle, such as bears the eye in 
allied groups, and with no appearance of any organ of vision 
or bulbus whatever. Behind the head a thickened ridge, 
containing a large vessel, takes origin and passes backward 
around the right mantle-edge, reaching nearly to the posterior 
median line; from this ridge depend fifty or sixty branchial 
leaflets resembling those of Patella, and not like those of 
Acmea or the Fissurellide; these leaflets are very large in 
proportion to the size of the animal, and gradually diminish 
posteriorly; they are slightly inclined outward; the anal 
papilla is very inconspicuous, opening between the line of the 
branchia and the head, a little to the right of the head; the 
intestine is much shorter than in the Patellidee, and coiled in 
much the same way through the very large greenish hepatic 
mass; this surrounds the ovary, which rises to the surface of 
the back in about its centre, and in this individual was crowded 
with eggs already in various stages of segmentation, and of 
about the size and general appearance of those of Acmea 
patina. 'The ovary appeared to be a single, simple, sac-like 
body of irregular contour as in Acmea ; no crop was noticed ; 
and the stomach seemed of very moderate size. 
Since but one specimen was available the observations were 
more or less imperfect, especially since the internal parts were 
somewhat softened. To obviate the extreme contraction 
caused by alcohol, the specimen was placed in water, with the 
result that it almost immediately swelled and became covered 
with an immense quantity of very slimy mucus, which ren- 
dered it almost impossible to handle, being so slippery ; and it 
had to be replaced in alcohol again to harden before the ex- 
amination could proceed. ‘The edge of the mantle is margi- 
nated with a rather broad thickened band, apparently without 
papille or other appendages of any kind. ‘The space occupied 
by the branchie is so large that the remainder of the animal 
is forced a good deal to the left in the aperture of the shell. 
The radula has a large, flat, ovate central tooth, with a 
thickened anterior edge, but no marked cusp; on each side of 
