232 The hish Naturalist December, 
from what is found in Machilis. The apex (fig. 6a, a) is 
stout and ribbed ; it spreads out into lamellar edges em- 
bracing the central process (6), which bears numerous 
blunt spines forming a " brush " ; internal to this are two 
acuminate processes {c, A) with minute irregular spines on 
their edges (Borner's Japanese species has four of these 
processes or "inner lamellae"). It is instructive to 
compare this lacinial head in an individual just after reach- 
ing full maturity (fig. 6a) with the corresponding structure 
in a specimen of the penultimate stage in which the apex, 
the brush, and the acuminate processes (fig. 6b, a, 6, c, d) 
have been worn down almost to their bases. Here, again, 
however, as in the case of the mandible, the new cuticle 
for the final instar with these structures all sharp and 
ready for use, can be seen inside. Except for its somewhat 
greater relative length, the maxillary head of P. maritimus 
hardly differs from that of P. brevistylis. 
References. 
igoS. — BoRNER, C. — CoUembolen aus Siidafrika, nebst einer Studie iiber 
die I. Maxille der CoUembolen. In Schultze's Forschimgsreise 
im westlichen und zentralen S ildafrika, Jena. 
191 3. — Carpenter, G. H. — Clare Island Survey. Part 32. Apterygota. 
Proc. R. Irish Acad., xxxi. 
ig32. — Latreille, p. A. — De I'Organisation exterieure et comparee de 
I'ordre des Thysanoures. Nouv. Ann. der Museum d'Histoire 
Naturelle, i., pp. 163-187. 
1809. — Leach, W. E. — Article " Entomology " in Brewster's Edinburgh 
Encyclopedia, ix. 
1873. — Lubbock, J. — Monograph of the Collembola and Thysanura. 
Ray Society. 
1886. — Oudemans, J. T. — Beitrage zur Kenntniss der Thysanuren und 
CoUembolen. Bijdr. tot de Dierkunde (Amsterdam). 
1904. — Silvestri, F. — Nuovi Generi e Specie di Machihdae. Redia, ii. 
ir)j J Contributo alia Conoscenza dei Machihdae dell' America 
Settentrionale. Boll. Lab. Zool. Portici, v. 
igo4. — Verhoeff, K. W. — Ueber vergleichende Morphologic des Kopfes 
niederer Insekten. AT^ofa. Acta. Acad., L'>op. Cayo^., Ixxxiv., no. i. 
, c) 10. — Ueber Felsenspringer, Machiloidea, 4 Aufsatz : Systematik 
und Orthomorphose. Zool. Anzeiger, xxxvi. 
Explanation of Plate 2. 
Structural details of Petrobius brevistylis. 
Fig. I. Diagram showing shapes and positions of compound eyes (c) 
lateral ocelli (o), and median ocellus {mo). x 28. 
2. Right mandible of female, hinder aspect, c, condyle ; a, apex 
m, molar area, x 28. 
