377 



and two on the other (as has been noticed in two other genera). 

 One of two specimens (sHde no. 26B33a) have notogastral plate 

 so broadly overlapping sides of ventral plate as to resemble the 

 condition found in Hypochthonius rufulus. This, therefore, is 

 clearly a reversion. The condition of three bristles on anal covers 

 is likewise a reversion to the more primitive condition. 



Propagation. — Females seem more numerous than males. The 

 eggs are packed two or three deep along postero-lateral walls of 

 abdomen to the number of ten though more usually six or eight. 

 Eggs appear as early as April 23 and continue at least until July 

 5. My August specimens are eggless. 



Identity. — Although difficult to identify the original figure 

 (Herman 1804, p. 92, pi. 4, fig. 5, B), a comparison with the 

 present figure a, especially as to the anterior horns (tectopedia 

 I), a development which seems to be a unique occurrence in 

 mid-European species, will serve to relate the type figure with 

 the present genus. The shape of the body as to rotundity or 

 ovalness varies with the angle at which it is viewed. Similarly 

 as to shape of pteromorphae, as seen from above, a comparison 

 of the accompanying figures 1 and 3 will show extremes of position 

 due to appression and extension of these parchmentlike elastic 

 expansions. The pteromorphae are well described as 'trigonal, 

 anteriorly truncated' (see PI. 19, fig. h). All specific characters 

 in the original description fit the present genus and species. The 

 drawing is crude. No major bristles are shown on the legs (!) 

 though adequately figured in B. 



The Regensberg figure (Koch 1835-44, fasc. 30/18) is uncon- 

 vincing, not only by comparison with 0. facula, but by the pos- 

 session of two bristles on posterior edge of abdomen. The 

 Italian description (Berlese 1882-1900, fasc. 3/4) differs in two 

 important respects: the pseudostigmatic organ is clavate (not 

 pedicelate) and the surface of the notogaster is minutely granu- 

 lose. 



0. orbicularis (Koch 1835-44, fasc. 3/6), type of Sphaerobates, 

 resembles this species considerably. 



It is surprising that, out of the 162 species recorded from the 

 British Islands, none should belong to this genus. 0. lapidaria 

 (Michael 1884, p. 230-233, pi. 5, fig. 1-5, pi. 23, fig. 6, pi. D, etc.) 

 is nearest. Between the distal ends of the lamellae (PI. 5, fig. 1) 



