Johnstonianidae — - Newell 
447 
found in the descriptions of the two forms. 
No adult of this species was found, de- 
spite extensive collections made at the type 
locality. 
Diplothrombium longipalpe Berlese 1887 
There is little in the original description of 
this species which can be relied upon to dis- 
tinguish critically between this form and the 
two species described here by the writer. The 
basal prominence of tarsus I appears to be 
significantly closer to the base of the segment 
than in D. monoense , but a similar prominence 
is found in approximately the same position 
in D. micidium. It is probable however that 
direct comparison of D. micidium and D. 
longipalpe would reveal reliable specific differ- 
ences. Berlese regarded the form named just 
below as a variety of D. longipalpe , but it is 
likely that if the differences Berlese noted 
were real that there are two distinct species. 
A complete bibliography of the species was 
given by Thor and Willmann (1947, p. 223). 
Diplothrombium septentrionale 
Berlese 1912, new combination 
This form was considered a variety of D. 
longipalpe , but it is almost certainly a distinct 
species. Again, the information available on 
this species in the literature is totally inade- 
quate to make any critical comparisons with 
the two new forms described in the present 
paper. 
Diplothrombium misellum Berlese 1918 
Berlese provided no figure of this species, 
but judging from his description (a single 
area sensilligera, anterior setae spiniform) this 
is not a Diplothrombium but probably a Cen- 
trotrombidium. Hence, it is provisionally placed 
in that genus, q.v. 
LASSENIINAE new subfamily 
diagnosis: Adults with anterior sensilla 
greatly reduced or of markedly different form 
from posterior sensilla. Pregenital tubercle 
present. Supracoxal setae present on coxa I 
and gnathosoma in both larva and adult. 
Larvae with anal sclerites. Deutorostral setae 
present; terminal seta of palp eupathi diform. 
Tarsi each with three claws. 
remarks: To each of the above statements 
should be added "in known forms." The 
group will have to be redefined as it becomes 
better known. 
Lassenia new genus 
ADULTS: Rather large mites, the known 
species between 1,000 and 1,700 /z in length, 
dark brown to brownish red. Scutum large, 
expanded, several times wider than the width 
of the crista metopica. Posterior sensilla elon- 
gate, slender; anterior sensilla variable in form, 
resembling the rest of the setae on the scutum 
so that they are sometimes not readily dis- 
cernible. Ocular plates bicorneate, protrud- 
ing, but not stalked. Dorsal setae of hystero- 
soma simple, smooth, stiff, rodlike in the 
known species, all of same type. Pars medialis 
of coxa I either present or absent. Coxal rings 
I and II both membranous dorsally, coxa I 
with supracoxal seta. Genital opening with 
three pairs of acetabula, guarded by a pair of 
crescentic genital sclerites and a pair of para- 
genital sclerites; a hemispherical or pedun- 
culate sclerite immediately anterior to the 
genital opening. Anal sclerites present. A 
characteristic Lassenia-otg&n anterior to coxa 
III. Base of gnathosoma with or without 
setae; supracoxal setae present. Proto-, deuto-, 
and tritorostral setae all present. Velum sim- 
ple. Chelicerae slightly to noticeably deflexed 
posteriorly. Palpi with five free segments, 
distal margin of trochanter deeply incised on 
anterior surface. Palpal tibia with heavy ter- 
minal seta, at the base of which is a single 
stout seta. Tarsus of palp with a single soleni- 
dion on posterior aspect which may be in 
either the basal or the distal half of the seg- 
ment; distal half of the tarsus richly supplied 
with eupathidia. Eupathidia present on all 
