516 F. M. MacFarrann, 
for the illustrations of the present paper, and for constant assistance 
in the preparation of microscopic sections. 
Types of the two new species here described are -deposited in 
the Museum of Invertebrate Zoology of Leland Stanford Junior 
University, and co-types will also be placed in the National Museum 
at Washington, D. C. 
Dironidae MAcFARLAnD Fam. Nov. 
Body aeolidiform, the foot wide, rounded in front, the tail 
pointed; oral tentacles absent; head with a large veil; cerata 
without cnidosacs, closely arranged along the sides of the 
dorsum and extending forward toward median line in front of 
rhinophores. Liverlobulate, withoutbranchesextending 
into the cerata; rhinophores perfoliate, without sheaths; anus on 
richt side near posterior end of body. 
Mandibles very large, the masticatory margin smooth. Radula 
teeth in five transverse rows. 
Dirona, MacFArLann Gen. Nor. 
Dirona MAacF. MS., ELIOT in COCKERELL and ELIOT, Notes on a Collection 
of Californian Nudibranchs, in: Journ. Malacology, 1905, Vol. 12 (3), 
p. 45. The British Nudibranchiate Mollusca, Part VIII (Supple- 
mentary), 1910, p. 69. 
Body broad, sub-depressed; head bearing a broad thin veil with 
smooth, undulating margin, in width equal to, or wider than, the 
foot; no oral tentacles; rhinophores perfoliate, non-retractile within 
sheaths; cerata large, inflated, non-caducous, arranged irregularly 
along margin of dorsum in a closely set series, which extends 
nearly to median line in front of the rhinophores. Cerata of varying 
size, the largest usually innermost, with smaller ones external to 
their bases; cenidosacs absent. Liver lobulated, but with no rami- 
fications to the cerata. Foot broad, rounded in front, tapering 
behind to a short tail. Anus at the summit of a conspicuous papilla 
far back, on right side, just below the cerata. 
Lip disk covered with thick-set, hair-like eutieular processes. 
Mandibles massive, the masticatory surface smooth, formed by a 
shield-like expansion which is reflected over the anterior margin of 
the mandible. 
Radula narrow, its formula 2-.1-2, the median tooth small, the 
