Ahdonteu in Laniatores 13 



value of "corona analis " (woodcuts figs. F — //) in Nemastomatoidae, and Troguloidse'. Thorell, 

 on the contrary (a p. 458), unhesitatingly interpreted the " anal plate " in Laniatores and in the 

 families Phalangioidaj and Ischyropsalidoidie amongst Palpatores, as well as the hindmost piece 

 in " corona analis " in NemastomatoidiB and Troguloidie, as a tergite, and accordingly counted 

 nine abdominal segments in Laniatores and Palpatores, in which view he was followed by 

 Simon (6, p. 118), though with some vacillation. 



As, however, several difficulties have to be solved, particularly as regards the sternites 

 in the order Opiliones generally, we have thought it well to subject the question to a 

 thorough examination. 



In the other orders of Arachnida, where the division of abdomen into segments is 

 clearly to be seen, tergites and sternites are placed opposite each other so plainly that 

 it is easy or, at any rate, not dithcult, to see which sternite belongs to each of the tergites. 

 But this is not the case in Opiliones where the sternites as a rule are not placed opposite 

 the corresponding tergites, so that it is impossible to find out which sternites belong to 

 each of the tergites without a comparative study of various animals. We shall therefore 

 examine in order the different combinations which occur. 



As regards Laniatores we may premise that we can speak with some confidence because 

 one of us has studied these animals for many years, and is acquainted with a considerably 

 larger number of them than have been described. Amongst the families of this sub-order 

 the very remarkable one, Oncopodoidse, established by Thorell, exhibits an arrangement 

 different from what occurs in any of the other families. Cephalothorax coalesces here with 

 the first eight- tergites of abdomen so as to form a dorsal shield on which the boundaries 

 of the tergites are marked by transverse grooves, operculum anale only remains free and is 

 situated on the under surface of the body ; at the same time all the sternites are fixed 

 into a ventral shield on which only six sternites, separated by shallow grooves, can be traced, 

 and of which the last does not exhibit any trace of bisection. In all other Laniatores 

 there are posteriorly three free tergites besides operculum anale : the latter is rather 

 large whilst the three free tergites in front of it are rather short, and diminish in 

 length gi-adually, but only a little, towards the posterior extremity of the body. On the 

 dorsal shield in front of the free tergites five transverse grooves are generally distinguishable, 

 of which the foremost, as already mentioned, marks the boundary between cephalothorax 

 and abdomen. The latter groove is, as a rule, distinct, but this is not alwa3's the case 

 with the others. It is curious that the fourth groove often disappears, although the others 



' We refer to the table of the families of Palpatores with tergites is the same as in Oncopin'. We believe that this 



their characters which will be found at the conclusion of this difference is fully explained by the fact that the animal 



part of our paper. described by Thorell was not fully grown, as he expressly 



■^ That such is the case in Oncopus Thor. and Gnomidtia states (/, p. 758), whilst this is the case with the specimen 



Thor. is clear from Thorell's descriptions of these genera examined by us. We therefore agree with Pocock (6, p. 283) 



(6, p. 134 and e, p. 378), but we have no doubt that it is the in assuming that the adult Pelitnus has the same arrangement 



case also with the only other genus yet described, belonging of the tergites as Oncopus. If this be so, Oncopodoidfe agree 



to this family, viz. Pelitnus Thor., although Thorell states with Cyphophthalmi in this point, that the young animals do 



in his description (/, p. 757) that the sixth and following not have all the tergites fused together, whatever be the case 



tergites are free. Partly through the kindness of Professor with the sternites. By the courtesy of Professor Thorell one 



Thorell we have been able to study both a representative of of us has had an opportunity of seeing a not fully grown 



Oncopus and a specimen which we refer to Pelitnus, be- Oncopus Fete Thor. in which the eight tergites had already 



cause it agrees in all respects with the definition of that coalesced with each other and with cephalothorax. 

 genus given by Thorell, except that the arrangement of the 



