Abdomen in Rieinulei 110 



points of insertion of ])owerful cylindrical muscles extending from the tergites to the sternites, 

 which by their action are drawn near to each other, thus flattening the abdomen. 



The tergite of the third segment is considerably shorter than that of the fourth, reaching 

 as it does no further forward than to the bottom of the deep groove (PL IX., hg. 1 f) in 

 front of the semilunarly emarginated line, which apparently constitutes the anterior margin of 

 the abdomen (compare PI. IX., fig. 1 / with PI. IX., fig. 1 a, C. Karschii: and PL VII., 

 fig. 2 a, G. plebeium). In the young specimen of Cryptostemma crassipalpe, which we have 

 dissected, we noticed at the bottom of this groove a narrow strip of softer integument, 

 forming a connecting membrane between the third and the second tergites. In adult 

 animals of Cryptostemma Karschii these two tergites seem to have coalesced, but the 

 boundary between them is marked by a line near the anterior corner of the abdomen, as 

 may be seen on Plate IX., fig. 1 f. The third tergite is, at least as a rule, divided into 

 a central area and two lateral ones'. The third sternite is so plainly seen on PL VII., 

 fig. 1 b and Plate IX., fig. 1 g that we need not treat of it further in this place. The 

 tergite of the second segment (PL IX., fig. 1 /, (/-) is quite short, in fact little more than 

 a crescent-shaped transverse strip. 



We have already mentioned that the abdomen is connected with the cephalothorax by 

 means of a peduncle which, however, is so short that it is scarcely visible in the normal 

 condition of the body, when the abdomen and the cephalothorax are coupled together. In 

 one of our specimens of C. Karschii, a male, the abdomen was broken off from the cejDhalo- 

 thorax, and though it was not in the best of conditions, we were thereby enabled to study 

 this part more closely. Amongst other particulars we noticed that the tergite (c^') of the 

 first abdominal segment, the peduncle, is of half the width of the posterior margin of the 

 third tergite (PL IX., fig. 1/). As in Araneffi^ and for the matter of that also in Ambly- 

 pygi', the principal firm element in the composition of the peduncle is the tergite of the 

 first abdominal segment. This is quite short, of about one-third of the width of the second 

 tergite, and does not consequently reach the sides of the peduncle. It is comparatively feebly 

 chitinized, and consequently only light brown in colour; it is connected with the surrounding 

 parts by means of a really soft and flexible connective membrane. In the young specimen of 

 C. crassipalpe we failed to discover with certainty any chitinized tergite in this place. 



In one of our specimens of C. Afzelii the abdomen was abnormally bent upwards so 

 much that the sternites of the two first abdominal segments were visible (PL VIII., fig. 2 g). 

 They (u' and v') are of about equal size, nearly crescent-shaped, their concave margins turning 

 against each other. They too are connected with the surrounding parts by means of a soft 

 very flexible connective membrane. It will appear from what we shall state below concerning 



are inserted on the tergites of the segments in front of the - In Arauese the sternite of the " peduncle " is generally 



fourth, appear to be directed forward, not from the dorsal to not chitinized. Cfr. Simon (e, pp. 4 — 6) and Sorensen (/). 

 the ventral surface. In Thelyphonus four pairs of muscular » Xn Amblypygi the sternite of the first abdominal seg- 



insertions are marked by depressions on the outside of four ment is but little developed (Sorensen, /); in Thelypho- 



sternites, viz. on those of the fifth to the eighth segments. noidie (Hansen b, p. 16.5) it is a broad, not particularly 



On the tergites seven pairs of depressions are noticeable, viz. short, very tirm plate ; in Tartarides (Hansen and Siirensen, 



on those of the second to the eighth segments. b) this plate is rather slightly chitinized, broad, but very 



1 In the youngest of our specimens of C. crassipalpe we short ; in Palpigradi (cf. Hansen and Sorensen, a, p. 232) the 



found the lateral arese of the fourth, fifth and sixth tergites first segment is very slightly chitinized, and, as is the case 



so weakly developed that they could scarcely be discerned ; with all the abdominal segments, not divided into tergites 



in the somewhat older specimen, which we dissected, the and sternites. 

 third tergite did not exhibit any lateral area. 



