546 A. E. Verrill— Catalogue of Marine Mollusca. 
ing a large groove. Proboscis very large, retractile, purple at the 
end, showing, when extended, the very broad radula, covered with 
very numerous sharp, hooked teeth, in many long curved rows. 
Foot broad and rounded anteriorly, with small auricles ; long ta- 
pered, and acute posteriorly, extending some distance beyond the 
mantle; a conical papilla near the tip above; under side, near the 
end, with a narrow, elongated, depressed, glandular area, surrounded 
by a raised border; this is sometimes tinged with bright red, in 
alcohol; the rest of the foot is usually tinged with chocolate-brown. 
Gill large, bipinnate, deep purple. This species grows to a great size. 
One from station 939, was over 5 inches (128™") long; 4 inches (102™™) 
wide; and about 2 inches (50™") high, even after preservation in 
alcohol. Off Martha’s Vineyard, stations 895, 939, 946, 1025, in 216 
to 258 fathoms. Off Delaware Bay, 1045, in 312 fathoms. At sta- 
tion 946, in 241 fathoms, seven young specimens were taken, some of 
them not over | inch long; these were associated with P. tarda. 
Pleurobranchea tarda Verrill. 
Plewrobranchea tarda Verrill, Amer. Journ. Sci., xx, pp. 392, 398, Nov., 1880; 
Proc. U. §. Nat. Mus., iii, p. 384, 1880. 
Puate LVIII, FIGuRE 26. 
In the best preserved specimens the reproductive organs are often 
protruded, the forms of the different organs varying with the state of 
extension. The verge or most anterior organ, when fully extended, 
is long, cylindrical or a little clavate, with rows of minute recurved 
hooks near the end, and terminated by a slender, curved spicule. 
The most posterior opening (urinal) is just at the anterior base of the 
gill, in the form of a small papilla, with a central opening. Between 
these there are two organs, on a more or less swollen common base ; 
the more anterior is a large opening with raised margin; ‘a little be- 
hind and below this is a long, exsert, flat, usually tapered and acute, 
copulatory organ, varying much in size and form according to the 
state of extension. All these organs can be so retracted as not to 
be noticeable, but this seldom happens in alcoholic specimens, most 
of which show the organs more or less extended. The anal orifice is 
behind the base of the gill. 
Taken in 1880, 20 miles south of Block Island (stations 814 to 
817), in 38 fathoms; about 70 to 100 miles south and southwest 
from Martha’s Vineyard (stations 865 to 879), in 65 to 192 fathoms, 
both on bottoms of mud and of fine, compact sand, very abundant 
