520 F. M. MacFarranp, 
margin a series of from two to four short, pointed denticles. Second 
lateral large, hamate, very much flattened, borne obliquely upon 
the margin of the radula groove, the tooth being strongly inclined, 
through its base being attached on its inner, lateral surface. Base 
long and slender and much curved to conform to the surface to 
which it is attached. Hook simple, strongly curved, blunt. 
Glans penis large, with thick-set papillae on sides. Spermato- 
theca large; oviduct slender and short. 
Habitat: Southern shore of Monterey Bay, California, and ad- 
jacent coast line, in tide pools of the littoral zone. Very rare. 
General Morphology of the Dironidae. 
Owing to the relative scarcity of Dirona albolineata and the 
abundance of Dirona pieta anatomical studies have been confined, in 
the main, to the latter species. No attempt will be made here to 
give a complete account of the morphology of these interesting ani- 
mals as that would necessarily exceed the limits of the present 
paper. Only the most striking features which justify their separation . 
as a distinet family can be taken up here. 
The general body form is practically the same in both species 
(Pl. 30 Figs. 1, 2), broad and but slightly flattened. On preservation 
in alcohol the form becomes markedly prismatic through shrinkage, 
resembling the Tritoniadae. The dorsum slopes rapidly forward and 
backward from the heart region. The head bears a broad velar 
expansion with an undulating margin. No trace of labial tentacles 
can be made out, though the velum is to be regarded, probably, as 
formed by a fusion of such structures. The anterior end of the foot 
is simply rounded, thickened, and undivided. Its increased thickness 
is due to the very large development of the glandular epithelium 
which everywhere characterizes the foot. 
The rhinophores are tall organs, arising from just within the 
inner row of cerata on the head, and are directed outward and for- 
ward. The clavus is conical, one-fourth to one-half the length of. 
the whole organ. Im Dirona albolineata (Pl. 32 Fig. 21) the clavus 
is regularly and deeply perfoliate, with about 16 to 20 leaves, united 
in front and behind in a median ridge. In Dirona pieta (Pl. 32 
Figs. 22 and 23) the clavus is of similar shape, but the perfoliation 
is irregular, the laminae being branched. 
Along the margins of the back at their junction with the sides, 
are borne the cerata, large inflated structures, with pointed apices, 
