2i 8 British Oribatidce: Notes on New and Critical Species. 
5. Cusp of lamellae projecting beyond base of lam. 
seta . . . . . . • piriformis. 
Do. do. not so projecting . . . . orbicularis. 
6. Translamella as broad as the cusp of lamella . . picipes. 
Do. much narrower than cusp of lamella oblongus. 
I have considerable doubt as to piriformis and orbicu- 
laris. In the form of the abdomen my species agree with 
Nicolet’s figures and the respective trivial names based on this 
character. But Nicolet, in describing his piriformis, says that 
the lamella terminates in an acute angle. If he is using the 
term ‘ acute ’ absolutely, of a sharp point, then my identi- 
fication is wrong, and there is a species which I have never 
seen, with piriform abdomen and pointed cusp. But Nicolet 
does not draw a pointed cusp in his figure (which is however, 
not a very helpful one in this respect), and I imagine he 
uses the word ‘ acute ’ in a relative sense, his object being 
to distinguish between orbicularis and piriformis. It is at 
any rate quite certain that the abdomen of my piriformis 
is piriform, agreeing with the outline of Nicolet’s figure 
exactly. Michael (Brit. Oribatidae) says of piriformis, 
‘ corner of the cusp outside the hair sharp-angled or pointed,’ 
but shews no points or angles in any of his figures. He 
says the cusp of orbicularis is ‘ truncated.’ I give figures to 
make it quite clear in what sense the two specific names 
are here used by me. 
Following Kulczynski I give the name picipes Koch to 
the commonest of all British forms in this group. Michael, 
without doubt, ascribing a wide variation to setosus Koch, 
included the much commoner form under that species. His 
figure gives a faithful representation of the cephalothorax 
of setosus and the abdomen of picipes. He even makes 
notatus Thor, a synonym of setosus, though (among other 
differences) Thorell’s species lacks the translamellar cusp — 
the acute point on the inside of the lamellar seta. Oblongus 
L. Koch (like notatus Thor., an arctic species) is much 
nearer to picipes, but has a narrower translamella, more 
slender pseudostigmatic organs, and the fore margin of 
the pteromorpha slanting slightly backwards instead of 
forwards. I have just recently met with Northumbrian 
specimens which I think are really oblongus L. Koch. If 
this determination be correct then there is a further difference 
in the dorsal integument — each mesh of the reticulation 
bears from 5 to 8 very visible punctures : also the dorsal hairs 
are shorter, though their arrangement and character seem 
much the same. 
I append a description of montivagus. 
O. MONTIVAGUS sp. n. (Plate A, fig. 3, 4; Plate B, fig. 12). 
Length about 700 . 
Naturalist, 
