Species of Opisthoplitlialmus. 133 



the anterior part of the carapace appears to rue to be an excellent 

 specific character. In some species, however (e.g., fossor), in which 

 it is usually absent, the fork may sometimes appear in a partially 

 developed form. 



2. A very important specific character is the general shape of the 

 hand in both sexes with regard to (i) the proportions of the width of 

 the hand to the length of the hand-back, and (ii) the convexity and, 

 to a lesser extent, the granulation of the upper surface. Although 

 the proportions may vary in specimens from different localities (e.g., 

 ( ivahlbergi and karrooensis), the variation appears never to be 

 very great. The length of the movable finger, on the contrary, 

 varies too much to be of specific value. 



3. The two secondary keels on the inner part :|: of the upper 

 surface of the hand are constantly present in some species, e.g., 

 fossor, macer, and constantly absent in others, e.g., chapcri, and 

 here form good specific characters. In others again, e.g., latimamis 

 ( calviis), these keels may be quite absent or well developed, even 

 in one and the same specimen. 



4. The finger-keel and the superior crest of the brachium is 

 subject to variation in many species ; in others, however, notably in 

 the capensis-granifrons group, the condition of the finger-keel is of 

 specific importance. 



5. A strong granulation on the mesial part of the ventral surface of 

 the abdominal segments is of considerable specific value. If, however, 

 this granulation be extremely fine or weak, although constantly 

 present in specimens from one locality, it may entirely disappear or 

 be replaced by a striated or wrinkled surface in a series of specimens 

 of the same species from another locality, e.g., in karrooensis. The 

 granulation on the lateral parts of the last abdominal sternite is very 

 variable and of no specific value. 



6. The presence or absence of a coarse granulation on the sides 

 of the carapace bordering the interocular area forms, as far as my 

 observations go, an excellent specific character. The granulation of 

 the interocular area itself is, however, rarely of importance, being 

 subject to great variation. 



7. As regards the position of the median eyes, such great varia- 

 tions have been noticed in some species, e.g., in gigas and glabrifrons, 

 that I have doubts as to the value of this character. 



8. With regard to the granulation of the crests of the cauda it 

 may be stated that, if the granulation be weak, it may be expected 



* The upper surface of the hand is divided by the finger-keel into an outer 

 and an inner part. 



