British Oribatidse. By A. D. Michael. 181 



It is very inconvenient that Nicolet should have used the name 

 of ovalis, as Koch used it before him for one of this genus which 

 Nicolet says is his punctata. Koch's description hardly seems to 

 me sufficient to distinguish ; the species are allied. 



50. Orebata quadricoknuta. Mihi, nov. sp., PL IV. Fig. 1. 



Average length about • 58 mm. 

 „ breadth „ '37 „ 

 „ length of legs of aU pairs about • 30 mm. 



This most complex species has in some respects considerable 

 resemblance to 0. setosa, but is difierent from, and cannot be 

 confounded with it ; indeed the peculiar form of the tectum alone 

 would distinguish this species at a glance from all that I am 

 acquainted with. It is difficult to give an idea of the elaborate 

 arrangements of the cephalotliorax by description. 



The whole form is a peai-shape, which, omitting the wing-like 

 expansions, is broadest not far from the posterior extremity ; the 

 broadest part of the wing-like expansions is about the middle of the 

 abdomen. The colour is chestnut-brown, with a vague lighter 

 patch at the extreme anterior portion of the abdomen, the legs 

 also are lighter. The chitinous hood of the forepart of the ros- 

 trum (PI. IV. Pig. 3) is rather narrow and arched, but with a 

 flattened, depressed anterior margin {h), bearing a minute median 

 point ; from thence the cephalothorax becomes broadly conical, but 

 it is almost concealed by the numerous projections or pieces of 

 apparatus (so to speak) which overshadow or surround it. By 

 far the most important of these is, as usual, the tectum (Fig. 1, 

 a, h) ; this, instead of appearing a single piece attached transversely 

 below or a little in front of the anterior margin of the abdomen, 

 looks as if it consisted of two symmetrical halves, or apparently 

 separate pieces, one on each side, only touching at a single point ; 

 in reality, however, they are joined near the base close to the line of 

 attachment to the cephalothorax, with which thoy here coalesce. This 

 line of coalescence, seen through the surface l)y the transparency of 

 the latttn', is oblique, extending from within the commencement of 

 the wing-like expansions of the alxlomen to about a tilth of the 

 distance along, and not far from the middle of, the cejihalothorax ; 

 thence starts the free inner edge of the half-tectum, almost at right 

 angles to the line of coalescence, and sweeps forward until it reaches 

 about the middle of the cephalothorax, where the two halves of the 

 tectum touch and then separate again. The lines of attachment 

 and lateral edges of the tectum are not straight, but form sweeping 

 curves. From the line of coalescence a thin, short ridge extends 

 inwards from each side, th(! two meeting. The result of all this is, 

 that the portion of the cephalotliorax cuclosed between the ti'ctum, 



