54 ON SOME RARE ARACHNIDS 



oval shape, but the sides are almost parallel. It extends 

 from the anterior end to about the middle of the dorsal surface, 

 but as it is rather narrow it does not occupy the whole breadth 

 of the abdomen. It is nearly squarely truncated behind in the 

 female, in which sex it is rather less in length than in the 

 male. In the latter sex the posterior border is slightly more 

 rounded. It is always covered sparsely with hairs similar to 

 those borne by the surrounding abdominal integument. This 

 structure is known as the dorsal scutum. On the ventral 

 surface there are two scuta, but these are much more of the 

 colour of the surrounding integument, and being obscured by 

 hairs, are in some specimens rather difficult to see. They are 

 of a pale yellowish brown colour, and do not contrast sharply 

 with the clay-coloured ventral surface. The arrangement of 

 these two scuta is quite different in the two sexes. 



In the female, the first or epigastric scutum covers the 

 epigastric region, and extends laterally over the pulmonary 

 sacs to completely embrace the pedicle. It terminates behind 

 in a slightly concave border which forms the anterior boundary 

 of the long transverse rima genitalis or sexual aperture. 

 On each side of its lower border it bears a spiracle, 

 which looks downwards, slightly backwards and outwards, 

 and which opens into a pulmonary sac. The rima is bounded 

 behind by the ventral scutum. This is short and semicircular. 

 The anterior border is nearly straight, and bounds behind the 

 rima genitalis. The posterior border is convex, and is con- 

 tinuous with the chitinous lips of each posterior spiracle. The 

 scutum is divided into two parts by a prominent, boat-shaped, 

 downwardly directed process. On each side this is continued 

 into a ridge running transversely outward. At a point about 

 two-thirds of the distance between the centre of the scutum 

 and its lateral border each ridge terminates in a minute pore- 

 like aperture. With a one inch objective these appear as 

 black dots. On a specimen eviscerated, treated with liquor 

 potassse, and examined in glycerine, each was seen to be the 

 aperture of a tube-like organ seated under the chitin of 

 the scutum. These apertures possess prominent chitinous 



