448 
PACIFIC SCIENCE, Vol. XI, October, 1957 
segments of all legs beyond the basifemur, 
sometimes present on ventral surface of telo- 
femur, patella and tibia I. Vestigial setae pres- 
ent on patella I and II and tibia I, but absent 
on tibia II. Solenidiai, S 2 and s 4 generally in- 
distinguishable, so that in effect only two 
solenidiai types are present on the legs. All 
tarsi essentially lacking claw fossa; IV with- 
out a posterior eupathid in terminal l/10th 
of segment. 
larva: Parasitic upon Diptera living in 
subaquatic environments. Scutum of known 
species with a pair of long posterior, and a 
pair of shorter anterior sensilla, plus two pairs 
of other setae near the anterolateral and pos- 
terolateral corners of plate; anterior sensilla 
sometimes set off on a minute sclerite sep- 
arate from the rest of the scutum. Crista 
absent. Dorsal setae variable in number, borne 
on individual setigerous sclerites. Ocular 
plates bicorneate. Coxae I with two pairs of 
setae, II with one or two pairs of setae, and 
III with two or three pairs of setae; a well- 
developed Lassenia - organ anterior to coxa III. 
Urpore present. Anal sclerites with two pairs 
of setae in known species. Base of gnathosoma 
with only the supracoxal setae, rostrum with 
protorostral, deutorostral and tritorostral setae 
present and well developed. Palpi somewhat 
geniculate, femur considerably heavier than 
rest of segments, and sometimes incompletely 
separated from patella. Tibia with heavy uni- 
dentate or bidentate seta at tip. Tarsus of 
palp elongate, cylindrical, with a single soleni- 
dion posteriorly, a terminal and subterminal 
eupathid. Femur of legs undivided, legs with 
only five free segments beyond the coxae. 
Vestigial setae present on patella I, II, and 
tibia I, but absent from tibia II. Tibia I with 
two types of solenidia, s 3 and s 4 , the latter 
larger than the former, with distinct internal 
structure, and a basal companion seta. Soleni- 
dion 4 also with a basal companion seta, S 2 
without a companion seta. Dorsal eupathid 
of tarsi I and II with a basal companion seta. 
All tarsi tridactyl, the median claw consider- 
ably longer, more slender, and erect than the 
lateral claws. 
TYPE species: Lassenia lasseni new species. 
remarks: The forms described under this 
genus have many features in common, but 
there are also a few in which they differ 
markedly. It is possible that these may even- 
tually necessitate the creation of a discrete 
genus for L. spinifera , although at present this 
does not seem necessary. 
For a while it was felt that this genus and 
Polydiscia Methlagl 1928 might be identical. 
Judging from the original description of the 
latter genus, this might be so, but the possi- 
bility is sufficiently remote to make a final 
decision unwarranted until Polydiscia squamata 
has been fully described. 
Lassenia lasseni new species 
male: Body (Fig. 181) 1,534 to 1,716 /x 
long to tip of propodosoma, 936 to 1,144 /jl 
wide, length/width = 1.44-1.64; average of 
five specimens 1,628 /x long, 1,066 /x wide, 
length/width = 1.53. Scutum (Fig. 183) 
broad, truncate posteriorly, rounded ante- 
riorly, with a single pair of very slender 
smooth sensilla arising from coarse alveoli. 
Otherwise with seven to nine stiff, stout, 
setae on either side of the mid-line; these setae 
slightly fusiform and smooth. Crista metopica 
well developed, extending from posterior 
margin to a point a little more than half way 
between the alveoli of the sensilla and the 
anterior margin of the plate. Cuticle of scu- 
tum coarsely punctate except for the pale 
posterolateral portion of the plate. With the 
exception of the sensilla all of the setae of the 
scutum are of the same type. Ocular plates 
well developed and bearing two corneae, the 
anterior one the larger of the two. A single 
seta arising from a very minute sclerite be- 
tween the ocular plate and the scutum; other- 
wise dorsum of propodosoma devoid of setae. 
Dorsal body setae (Fig. 184) stiff, smooth, 
straight, each arising from a small sclerite. 
Cuticle of dorsum smooth, without striae. 
Coxa I (Fig. 192) with 45 to 50 smooth, slen- 
der setae plus the short, blunt, spikelike supra- 
