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PACIFIC SCIENCE, Vol. XI, October, 1957 
adult terrestrial Parasitengona (Figs. 54, 82, 
154, 192). In many cases, especially in the 
adult, it is difficult to tell whether this is a 
part of coxa I or II, or whether it is a distinct 
sclerotized area independent of the coxae. 
However, in those species in which coxae I 
and II are rather distinctly separated, and in 
which a distinct pars medialis coxae is de- 
veloped, it is clear that this is an extension 
of the coxa of leg I. In those cases in which 
the relationship is not so clear, it is probably 
safe to assume that the pars medialis coxae 
is morphologically a part of coxa I rather 
than II. 
The number of setae present on the pars 
medialis coxae is quite variable even within 
the limits of a given species. At best, varia- 
tions in this structure appear to be of a 
specific rather than a generic nature. An in- 
teresting variant is found in the genus Las- 
senia , in which L. lasseni has a well-defined 
pars medialis coxae in the adult (Fig. 192) 
whereas in L. spinifera (Fig. 234) the pars is 
entirely absent. In the latter species there is 
a general reduction in the degree of sclero- 
tization of the coxae for many of the setae 
which normally would be included within 
coxae II actually lie in the membranous cu- 
ticle immediately behind the posterior margin 
of these (Fig. 234). It is interesting to note 
that when there is a difference in the form of 
the setae of coxae I and the intercoxal area 
such as exists in Diplothrombium micidium 
(Fig. 154) and Lassenia lasseni (Fig. 192) the 
setae of the pars medialis coxae are more 
similar to those of the intercoxal area than 
they are to those of the coxae themselves. 
Coxal Ring 
In the Parasitengona, the coxae have be- 
come largely incorporated into the ventro- 
lateral body wall as a series of well-defined 
plates. However, if one examines the distal 
portion of the typical coxa of an adult it is 
found that this comprises a cylinder of ex- 
tremely short length, and it is this peripheral 
portion which the author refers to as the coxal 
ring. The distal portion of the coxa is ringlike 
in the adults of most species of terrestrial 
Parasitengona, except for leg I, in which the 
coxal ring is generally, if not always, incom- 
plete dorsally (Fig. 107b). This is the situation 
in the adults of all genera except Lassenia , in 
which the two known species have both coxal 
rings I and II incomplete dorsally in the adult 
(Fig. 232). In all species of all genera of the 
Johnstonianidae, coxal rings III and IV are 
complete dorsally (Fig. 107a). 
Urpore 
The urpore is present in the larvae of all 
known species of Johnstonianidae and is well 
developed. There are no variants of known 
generic significance. 
Lassenia Organ 
This is a term which the author has applied 
to a structure of unknown nature and function 
immediately anterior to coxa III of larvae and 
adults of certain of the Johnstonianidae. It is 
especially well developed in Lassenia lasseni 
and Lassenia scutellata (Figs. 199, 209, 221, 
251). A search of specimens of Johnstoniana 
and Centrotrombidium has failed to reveal a 
corresponding organ in these genera. At least 
a rudiment of this organ is found in larvae of 
Diplothrombium monoense , and D. cascadense , 
but not as yet in the adults of these species. 
A systematic search of other Parasitengona 
might reveal other groups in which this organ 
is found. It is most likely a gland of unknown 
function for in a number of specimens, both 
larva and adult, a duct leads from the body 
surface into the incompletely hydrolyzed re- 
mains of a glandlike mass of cells. Beyond 
this its nature is unknown. 
Genital and Paragenital Sclerites of Adult 
The Johnstonianidae are somewhat unusual 
among the Parasitengona in that the genital 
and paragenital sclerites are almost equally 
developed. Thus the genital opening is sur- 
rounded by four sclerites of very nearly equal 
size, and bearing roughly equal numbers of 
