FOLSOM: MOUTH-PARTS OF ANURIDA MARITIMA. 105 
The agreement between the finished mandibles of Campodea and 
Japyx, on the one hand, and Collembola, as represented by Anurida and 
Orchesella, on the other hand, is remarkably close. In both groups the 
mandible is hollow, has an oblique basal opening, which is large in Cam- 
podea, and, instead of an ordinary articulation, a free basal pivot, which 
is peculiar to the Apterygota. The homologies extend further, for I 
find that the similar and complicated movements of the mandibles are 
actually effected by muscles which are probably homologous in the two 
groups. The equivalence of certain muscles in Campodea, as repre- 
sented by Meinert (65, Taf. XIV., Figure 15) with others figured by 
myself for Orchesella (Folsom, ’99, Plate 2, Figures 14, 15) may be ex- 
pressed in tabular form as follows : — 
Campodea (Meinert). Orchesella (Folsom). 
Muscle C’ (distal) corresponds with 9. add. 
«_ C (proximal) ae Sa eforrotil. 
< -D «6 xe 5. prt.t. and 6. prt. ms. 
oe as) D; G se 3. ret. rot. and 4. ret., or else 7. rot. 
and 8. rot. 
The incompleteness of Meinert’s figure prevents as exact a comparison 
as is desirable. 
Japyx is nearest Campodea in structure, and the mandibles of Japyx, 
which have been described and figured by Meinert (65), Grassi (’86°), 
and v. Stummer-Traunfels (91), are essentially like those of Campodea, 
but lack the articulated lacinial lobe, there being a lacinial region, how- 
ever, which (Grassi, ’86°, Taf. II., Figura 14) is separated by a trans- 
verse line from the fulcrum. The muscles of Japyx agree with those of 
Campodea, and it is to be noted that the adductors originate upon a 
median chitinous plate, or tentorium, just as in Collembola, but not as 
in Orthoptera. The muscle f of Meinert (65, Taf. XIV., Figuren 5, 15) 
has no homologue, it should be said, among the mandibular muscles of 
Orchesella, and I should be disposed to regard it as an adductor of the 
head of the first maxilla, had not v. Stummer-Traunfels (91, Taf. I, 
Figuren 1, 3) figured the tendon of the same muscle in Campodea and 
Japyx going to the mandible. This author (91, p. 220) erroneously 
states that the adductors of Collembola, Campodea, and Japyx are at- 
tached to the “ Stiitzapparate,” by which he means the lingual stalks 
(Plate 6, Figure 38, pd.) ; these, however, are quite distinct from the 
tentorium, which he apparently overlooked. 
Nearly allied to the entognathous genera Campodea and Japyx are 
the ectognathous genera Lepisma and Machilis. In Lepisma the early 
