The true first ahdomhial Sternite 17 



of the so-called first sternite which we have been discussing, that is, in tlie same place as 

 in Cyphophthalmi and Laniatores. These facts tlirow light also on the structure of CyphOph- 

 thahni. We mentioned above (p. 12) in this chapter that in young ■ animals of that group 

 the spiracles are placed on a pair of lateral pieces of chitine which are separated from the 

 surrounding parts by soft skin (PI. II., fig. 3 h ; PI. III., fig. 4 c), and these correspond evidently 

 to the foremost pair of lateral pieces in the species above mentioned of Gagrella, Sclerosoma 

 and allied genera. In the adult Cyphophthalmi, moreover, the foremost of the oblique 

 grooves sweep forward along the inner side of the spiracles^ which means that here the 

 separation between the anterior pair of lateral pieces of the so-called first sternite and the 

 surrounding parts, remains longer than the separation between the two sternites of which the 

 so-called first sternite is composed. 



In speaking of how many sternites we have been able to account for, we have hitherto 

 treated the numbers which we have made use of as merely preliminary, because in all divisions 

 of Opiliones we can account for one sternite more, the true first sternite, which is represented 

 by what we have called "arculi genitales" {m on the woodcuts). These are found in all members 

 of the order, often easily observed, or even of considerable size, though in a large number of 

 cases only a small part of them preserves so much indejjeudence that it can be demonstrated. 



In Phalangioidas with soft integuments, as in Phalangium, we meet with a peculiar 

 feature which hitherto has received but little attention and remained without an e.'cplanation, 

 viz. that though the fourth pair of coxse are separated from abdomen in the greater part 

 of their extent by the groove in the posterior wall of which the spiracles are situated, 

 they are nevertheless, if we may say so, intimately united to abdomen at their proximal 

 extremity along the lateral margin of operculum genitale (woodcut fig. A); anteriorly this 

 apparent part (m) of the coxa is continued as a narrow band along the proximal extremity 

 of the third pair of coxse, towards, or even reaching, the anterior extremity of operculum 

 genitale. 



This peculiar arrangement by which the fourth pair of coxse is rendered less movable 

 than the others has of course been noticed by earlier observers-, but it does not appear to 

 have received the attention it deserves^ 



In Phalangioidse with harder integuments, as in Sclerosoma (woodcut fig. E) and in 

 Gagrella (woodcut fig. D) with its congeners, the same ari-angement exists, but this continu- 

 ation or apparent inner portion of the fourth coxa is separated by a groove, a suture or a 

 strip of soft skin, not only from the part of abdomen which lies behind it, but also from 

 that part of the coxa which is separated from abdomen by the deep groove, in the posterior 

 wall of which the spiracles are situated. In all Cyphophthalmi with which we are acquainted 

 the same structure is met with : operculum genitale is literally framed by a pair of pieces 



' It must be borne in mind that in Cyphophthalmi the Phalangium Opilio L. (6, PI. XXI., fig. 3) and Sclerosoma 



spiracles are in an uncovered position on the ventral surface, quadrUlentatmn Cuv. {ibitl. fig. 9). 



not placed in a groove between the fourth coxa and abdomen ■' Sorensen had noticed it in 1873, but was uuable to 



as they are in the majority of Palpatores, for instance in all arrive at an explanation of it, because at that time the 



Phalangioidffi. Museum at Copenhagen was rather poor in Phalangioidae 



- It is for instance represented, though not quite true to with hard integuments, and did not possess any Cyphoph- 



nature, in one of Treviranus' figures of Phalangium parte- thalmi at all. 

 tinum De Geer (P!. II., fig. 11); Simon too shows it in 



s. 3 



