COMPAEATIVE MORPHOLOGY OF THE GALEODID^. 311 



phonus nuncivs (65) (reproduced in PI. XXVII. fig. 10) to see that this conjecture is correct. The animal 

 had apparently lost its eyes, but the region where the eyes normally are in Scorpions is seen to be an island 

 of the original dorsal surface, gradually being grown over by the cephalic lobes which, in all modem 

 Arachnids, have closed together in the middle line. The ocular tubercle must then be considered to be 

 a primitive feature. And it is worth recording that, of the Aranese, the Aviculariidse, which alone 

 retain an optic tubercle, have also retained other primitive features, e. r/. the coxal glands. 



Segmentation of the Dorsal Surface : Abdomen. — The tergites of the abdomen continue 

 without change, except in the matter of size, the series begun by those of segments 5 and 

 G of the cephalothorax (PI. XXVII. fig. 1). As a rule, the tergites gradually decrease 

 in size towards the anal segment. Ithax, however, is a remarkable exception, the terga 

 towards the posterior end of the hody gradually widening until the large anal segment 

 is completely encircled {cf. fig. 13). It is, however, not certain here whether this 

 great encircling plate of the anal segment is really morphologically a tergum. The 

 tergites are, functionally, only more rigid areas of the cuticle for the protection of the 

 circulatory mechanism. The lateral extensions of these areas at the posterior eud of the 

 body in Ehas may be for the protection of the defenceless end of the body from eaemies. 

 The ventral position of the anus in this genus is in keeping with this suggestion. 



Segmentation of the Ventral Surface. — Although there are no structures like the 

 cephaHc lobes to disturb the segmentation ventrally, it requires a considerable amount 

 of ektcidation. The first segment has practically disappeared from the ventral surface, 

 while the limbs which belong to it have been shifted up dorsally above the mouth. 

 Consequently the 2nd pair of a2)pendages become the most anterior pair of limbs 

 ventrally, and have moved forward to the anterior end of the ventral surface. This 

 forward shifting of the pedipalps has apparently forced the ventral portion of the 

 1st segment still iurther forward, to form the " labium," or lower half of the beak, which 

 will be described presently. In the majority of Galeodidse, this " labium " or sternal 

 surface of the 1st segment is no longer visible from the ventral surface, but in the genus 

 Solpuga the relations can still be made out (PI. XXVII. fig. 14). 



The second segment is the first obvious component of the ventral surface (figs. 14 and 

 15), and this is followed by a complete series to the end of the body. The most remark- 

 able feature in these ventral surfaces of the segments is the almost complete absence of the 

 sternites. This obliteration of the sternites along the thorax is due to the coxae of the 

 legs meeting in the middle line, and there is evidence to show that, along the abdomen, 

 the areas which appear to be sternites are really the remains of limbs, also meeting 

 in the middle line, which have now flattened down to form part of the body-wall 

 {cf. section on tlie abdominal limbs, p. 328). 



The remains of sternites in the Galeodidse are very slight. We can make out the 

 remains of three sternites, which are visible in Solpuga (fig. 14); i. e. of the fii'st three 

 segments. These together form a long plate, which, anteriorly, supports the labium, and 

 ends posteriorly between the coxse of the third pair of appendages. This posterior butt- 

 end of the plate is often the only part of it visible from below. The only other remains 

 ^f a sternite in Galeodes is perhaps the triangular piece which occurs in front of the 

 genital operculum, between the coxae of the last pair of legs. These coxae, sloping forward, 

 would perhaps allow the sternite to persist in the angle between them. 



