1881. | Scolopendrella and its Position in Nature. 701 
in Campodea; the labrum is small and rounded in front (what 
Menge calls the labrum is in reality the clypeus). The mode of 
insertion of the antennz and their shape is as in Campodea. The 
form of the clypeus and of the antenne are entirely unlike those 
of any Myriopod known to us. The mouth-parts bear the same 
relation to the head, and are sunken or withdrawn into the head 
in the same peculiar manner, as according to Meinert and our 
own repeated observations, characterizes the Thysanura, The 
bases of the jaws and maxilla are contained deep in the cavity of 
the head or epicranium, only*the ends projecting out, as in Cam- 
podea.* The mandibles are slightly curved, toothed, and con- 
structed on the Campodea type; the maxilla are long and slen- 
der, and in a side view are seen through the walls of the thin 
€picranium, appearing much as in Campodea. Their structure is 
in general like that of Campodea. 
The legs are five-jointed and, as observed by Menge and 
Ryder, end in two claws, as in Campodea; in Myriopods there 
are six joints, and always a single large claw. The stigmata we- 
nave found to open between and just behind the legs, as Mr. 
Ryder has stated, but we have been unable to find any in the first 
and second segments behind the head; those corresponding to 
the prothoracic and mesothoracic segments of hexapodous in- 
sects, , 
The v-shaped opening, supposed to be either sexual or to cor- 
respond to the sucking organ of Thysanura, we have observed 
Only in the fourth segment, or that corresponding to the first 
abdominal segment of Thysanura and insects in general. We 
are disposed to regard this as the homologue of the sucker of 
*Meinert (Annals and Mag. Nat. Hist. 1867, p. 362), ascribes great importance to 
the “ position of thé first two pairs of appendages of the mouth with reference to the 
wll”? In most insects,and in the Myriopods, the jaws for example act transversely 
and articulate with the epicranium by means of a hinge-joint. In the Thysanura the 
bases of the mandibles and maxillz are retracted within the cavity of the epicranium, 
and are buried in muscles, while generally only their points project outside of their 
Mouth. This is the case with Thysanura, both in Campodea and allies (our sub- 
Order Cinura), and in the Podure, or Collembola, but in the highest Thysanura, 
Lepisma, the jaws are external and articulated to the skull outside of the mouth, 
and thus Lepisma approaches the true hexapod insects, and affords a passage from 
ene type of head to the other, Scolopendrella, with its feeble jaws and maxillz 
buried in the mouth and enveloped in muscles, is throughout Campodea-like, and 
€ssentially unlike the Myriopods, such as Lithobius and Scolopendra with their 
Ss Powerful, biting jaws, hinged to the thick, solid epicranium and acting trans- 
rersely, 
