Abdomen in Palpatores 15 



anale, are likewise as a rule free, but their movability decreases towards the fore end so 

 that very frequently the sixth tergite cannot be said to be capable of free movement 

 against the fifth. This is the case even in some species of Gagrellini, which have hard 

 skin. And the sixth and seventh tergites are even fused with the dorsal shield in Melanopa 

 ti'istis Thor. as well as in a probably undescribed form from California in the Museum of 

 Copenhagen, which approaches nearly to the genus Egwnus C. L. Koch and possesses rather 

 hard integument. We have already mentioned that all the tergites are free in both sexes 

 of Ischyropsalis Millleri and, according to Simon, in the male of /. nodi/era E. S. It remains 

 to be added that in Sclerosoma and allied genera the three last tergites (not counting operculum 

 anale) are bent downwards on to the under surface of the body (woodcut fig. E), in such 

 a way that the fifth tergite forms a rather sharp corner with the succeeding one, and appears 

 to terminate the body, when viewed from above. In Troguloidaa the same is the case with the 

 two last tergites (not counting operculum anale), and the sixth tergite is apparently the 

 last. In Phalangium and allied genera and in Ischyropsalidoidffi, the posterior extremity of 

 abdomen is, on the contrary, gently rounded down, so that only operculum anale can be 

 said to be placed positively on the ventral side (woodcuts figs. G and D). In this respect 

 Nemastomatoidffi occupy an intermediate position, the three last tergites (besides operculum 

 anale) being bent downward, when the body is not distended by food or eggs. 



Whilst thus the number of tergites in abdomen is very constant in Palpatores, this 

 is well known not to be the case as regards the sternites ; because the " corona analis," 

 which is well developed in Nemastomatoid;e and Troguloida3 (woodcuts figs. F, G, H), is 

 either absent or much reduced in Ischyropsalidoidaj and Phalangioidse. Apart from this differ- 

 ence it may be said, at any rate if we follow the statements hitherto published, that all 

 Palpatores possess five distinct sternites, even though these may be separated from each other 

 only by folds of the skin, such as is frequently the case in species of Phalangioidse which 

 have soft skin. The sternite, which according to this view would be called the first, extends 

 more or less far between the coxae and terminates in an operculum genitale, which always 

 closes the genital orifice. Operculum genitale {r) is of somewhat different shape in different 

 groups. In Phalangioidse (woodcuts figs. A, D, and E) it is very large, its posterior extremity 

 being not far from the posterior margin of the " first " sternite, to which it belongs, whilst its 

 lateral margins are slightly concave in the greater part of their extent ; in those with hard 

 skin, as in Gagrella, Sclerosoma and geneia allied to them, it is sharply separated from the 

 rest of the sternite by soft connecting skin ; in Phalangium and congeners, where the general 

 integument is soft, operculum genitale is likewise separated from the sternite, but not so con- 

 spicuously. This difference, which in itself is of little consequence, has caused Simon (6, p. 1.58) 

 to reckon six sternites in Sclerosoma and allied genera, but only five in those whose skin 

 is softer, he having mistaken the soft connecting membrane between operculum genitale and 

 the rest of the sternite in the hard-skinned genera, for a boundary between two sternites. 

 In Ischyropsalis, Nemastomatoida' and Dicranolasmatini (a group of Troguloidre) operculum 

 genitale is on the contrary small, its posterior margin being situated far forward near the 

 anterior extremity of the fourth pair of coxae. Its lateral margin is convex both in the 

 genera mentioned and in Trogulini (woodcut fig. F) where it is very small, and so short 

 that in both sexes it is several times as broad as it is long. 



It is, however, always possible to show that this foremost sternite really consists of 

 two sternites fused together. Immediately behind each of those grooves which separate the 



