PLEUROBRANCHUS. 201 
large pad in front of the gill, the male organ projecting from the 
front of the orifice. Length 20, width 15 mill. 
Shell noticeably chalky, with thin corneous edges, contained in 
the interior of the mantle, depressed, nearly smooth, reddish-yellow, 
oval, growing obliquely as in other species; length 8 mill. (Orb.). 
Coast of Ensenada de Ros, 41° S. Lat., east coast of Argentina, 
under large stones at low water (Orb.). 
P. patagonicus ORBIGNY, Voy. dans |’Amér. Mérid., p. 204, pl. 
ye {./4, 5. 
Differs from other described species in the large size and quad- 
rangular shape of the foot, and small extent of the mantle. 
P. piguETI Rochebrune. PI. 54, figs. 98, 99, 1, 2. 
Body rounded, ovate, swollen; mantle ovate, subtruncate in 
front, the margins waved, wide; foot rather narrow, circularly 
crenulated , buccal region proboscis-like ; tentacles 2, round and 
channelled ; gills somewhat concealed ; scarlet above, buff-white be- 
low. Length 22, width 16, alt. 12 mill. (Rochebr.). 
Mogote, Bay of La Paz, Lower California (Diguet). 
Pleurobranchus digueti RocHEBR., Bull. Mus. d’Hist. Nat., 1895, 
p. 240. 
Differs from P. patagonicus d’Orb. by its oval, rounded and not 
quadrilateral body ; narrow foot, not extending beyond the other 
parts of body; by the proboscis-like, not rounded head, round in- 
stead of flattened tentacles, the partly covered gill not passing 
beyond the edge of the mantle, and by its coloration. (Rochebrune). 
A specimen collected at La Paz by Mr. W. K. Fisher, and pre- 
sented to the Academy by W. N. Lockington, seems to belong to 
this species. It is illustrated on pl. 54, figs. 98, 99, 1, 2, and may 
be described as follows : 
Color, after long immersion in alcohol, dirty light gray, bluish 
over the viscera. Dorsal integument warty, the warts small, sepa- 
rated, appearing as if planted in little pits. Mantle wider than 
foot, amply projecting on all sides. Eyes behind bases of rhino- 
phores, under the mantle. Rhinophores close together, short, 
blunt, cylindric and slit as usual; below them a trilobed anterior 
disk around the mouth. Foot longer than body, with the forward 
margin duplicated. Gill folded, adnate, except for a short free tip, 
with about 20 bipinnate plumules on each side, alternating on the 
rachis which bears a tubercle at the insertion of each plumule. 
