The nudibranch family Dironidae. 519 
clavus conical, deeply perfoliate, about one-half the length of the 
whole rhinophore. Cerata lanceolate, inflated, entirely smooth, some- 
what flattened antero-posteriorly, arranged in closely set, irregular 
series along each margin of the dorsum. The largest cerata are 
innermost and may reach one-fourth to one-half the length of the 
animal, smaller ones are arranged externally to these in close, but 
irregular series. Cerata continued forward in front of the rhino- 
phores toward the median line of head but do not meet. The two 
lateral series meet posteriorly above the tail. No enidosacs present. 
No branches of the liver extending into the cerata. 
Reproductive openings two, situated as usual, inconspicuous. 
Renal opening minute, immediately below the cerata, a short distance 
behind the reproductive openings. Anal opening at summit of a 
eylindro-conical papilla, far back on right side, in the line of the 
outermost cerata, near the posterior end of the body. 
Color (Pl. 30 Fig. 2) everywhere a beautiful translucent grey, 
save for a narrow band of pure white edging the veil, the lateral 
mareins of the cerata, the median crest of the tail, and passing 
from the inner base of the clavus of each rhinophore down the 
inner side of its stalk and uniting in a transverse line across the 
head. Along the upper, right side, just below the bases of the 
cerata and extending from immediately behind the reproductive 
openings to the posterior end of the dorsum is a broad, whitish 
band, conspicuous in alcoholie material, due to a strongly developed 
glandular zone. In large individuals the body and cerata are oc- 
casionally also flecked with minute spots of pure white. The dark 
liver shows through the integument. 
Total length up to 42 mm, height 8 mm, width 7 mm. 
Mandibles strong and massive, in general similar to those of 
Dirona picta, the boundary between the upper and lower portions 
of the inner face of the wing being less strongly marked. 
Radula formula 2-.1:2x29—32. Teeth similar in form to those 
of Dirona picta, but the laterals much larger. Median tooth almost 
rudimentary, at the bottom of a deep groove, its base rounded in 
front, squarish behind, in side view triangular, its upper surface 
prolonged into a straight spine, which is often finely grooved on 
its upper surface. First lateral tooth depressed, nearly horizontal. 
Base elongated, nearly linear, the ends rounded, above prolonged 
posteriorly in a stout spine, which rises but slightly above the plane 
of the upper surface of the basal portion. Upon the inner basal 
