Oribatidae 



in the genera Neoliodes, Nothrus and Hypochthonius there is often a certain 

 resemblance. Legs fitted for walking or crawling, except in the genus 

 Zetorchestes, where the fourth pair are fitted for jumping. The Nph. often, 

 and the Im. less frequently, carry on the dorsal surface of the Abdomen the 

 abdominal portions of the dorsal skins cast at all prior ecdyses, they are 

 usually earned concentrically ; when they are present the age of the creature 

 may be known by the number of cast skins. In some few species the 

 external layer of the cuticle of the Im. (the epiostracum) is easily detched 

 and is apt to be rubbed off, either wholly or more frequently partly, from 

 the dorsal surface; it generally bears all the markings, so that when it is 

 gone the cuticle of a rough species may appear smooth. 



XeglF 



Fig. i. Oribata dorsalis 

 Dorsal surface. 



The anatomy of the Ex o skeleton, so far as it is necessary for the 

 identification of species and for understanding this work, may be very 

 shortly sumarized as follows. The Cephalothorax (Cephth.) and Ab- 

 domen (Abd.) are usually divided by a well-marked constriction or trans- 



verse line between the second and 

 third legs; this demarcation however 

 is lost in the 2 genera Scutovertex 

 and Amerus, and almost lost in the 

 one species Tegeocranus vellatus. The 

 Cephth. of the Im. is usually firmly 

 anchylosed to the Abd., but that of 

 the immature creatures commonly 

 has a slight motion upon it. In the 

 one subfam. Phthiracarinae however 

 the Cephth. of the Im. is moveably 

 articulated to the Abd. and is capable 

 of being folded downward so that its 

 ventral surface then rests against the 

 ventral surface of the Abd. 

 The Cephalothorax (Cephth.) may be considered as divided into 

 two parts; an anterior part or Rostrum (Rost.) and a posterior part. 

 These are divided in many species by a trans- 

 verse line, which may probably be the horno- 

 logue of the cervical groove in Crustacea 

 (Huxley, Astacus); in many other species 

 however there is not any such line and it 

 would then not be possible to fix a posterior 

 limit to the Rost. 



The Rostrum (Rost.) is usually a 

 species of hood covering and protecting the 

 Trophi, its sides are called the Genae and 

 each Gena ends anteriorly in a small free 

 point in some few species, which is useful 

 in identification. The Rost. bears 2 curved 

 hairs, called the Rostral hairs (Rost. hairs). 

 The hood of the Rost. in partly closed 

 below by the articulated maxillary-lip (or 

 Hypostome), it is formed by the coalesced 

 bases of the maxillae, but the distal portions of the maxillae form large 

 projecting organs springing from, but at right-angles to, the lip. These 



Kasth.Xamh. 





. Anal covers 

 Dorsplate 



Fig. 2. Oribata orbicularis ( K i\). 

 Ventral surface. 



