Mr. J. Wood-Mason on Scolopendrella. 57 
in spirits, with the dorsal surface upwards the mandibles are 
visible beyond the sides of the head, between the oval sacs 
above described and the insertion of the antenne. They are 
therefore attached very far forwards ; and their strong articu- 
lation is rendered very conspicuous by the amber-like colour 
of the cuticle, both of their posterior extremity and of the part 
of the head into which this fits—amber-like coloration indi- 
cating the great firmness of the chitinization that has taken 
place. They are divided by a very distinct joint, visible just 
in front of the insertion of the antenne, into two segments: 
the first of these is a slightly curved prism attached to the 
head by its dorsal margin, and to the outer lobe of the four- 
lobed plate by its ventral margin, its inner side being conse- 
quently open, so as to give passage to the flexor muscles, 
which are inserted into the inner face of its outer wall; the 
second, a triangular plate, is armed on its inner side with two 
distinct series of teeth distinctly separated from one another 
by a rounded notch, the posterior series consisting of five 
small equal pale and blunt tubercular ones, and the anterior 
of four dark brown and highly indurated sharp teeth, of which 
the anterior and outer is slightly the largest, and lies in a 
different plane from the rest; from the bottom of the notch 
between the two series of teeth a faint groove encircles the 
joint, subdividing it into two, corresponding respectively to the 
first (which in Glomerds is developed on the inner side into 
an antero-posteriorly elongated molar process) and second or 
apical (which is bifureate*) free joints in Chilognatha gene- 
rally. ‘The mandibles can be readily disarticulated from the 
head, as also can their two principal joits from one another. 
They are, in short, built exactly upon the plan of those of the 
Chilognatha, being divided into three distinct joints, and 
therefore not consisting, as has been stated, of a single piece 
only. 
Second Pair of Postoral Appendages.—These are made up 
of seven or eight distinct sclerites, all united together by 
membrane, namely :—four lateral, of which two are long and 
* The apical joint in all Chilognatha consists of two parts attached to 
a common hbase (the first free joint), but lying in different planes and 
applied to each other, much as are the “galea” and “lacinia” of the first 
maxillz in such an insect as the common cockroach—an arrangement 
strongly suggestive of its being, like the jaws of Peripatus, a moditied 
pair of claws. The objection to this is that all living Myriopods except 
Scolopendrella have the legs terminated by a single claw; and it would 
be fatal were it not that the legs of the Protracheata are biunguiculate. 
The uniunguiculate condition of the legs in most Myriopods, in the larvee 
of many insects, and in all the Collembola is probably adaptive. 
