SCOEPIOXES. 



Xone of the seven segments of the legs are subdivided. The 

 seventh or apical segment (tarsus) is furnished on its lower side 

 with hairs or spines. Three claws are articulated to the membrane 

 at its distal end, two superior and one inferior, the latter being 

 often partially or wholly worn down. The upper side of the tarsus 

 is generally produced at its distal end into a process (the claw- 

 lobe) overhanging the base of the claws, and the claws are some- 

 times overlapped laterally by a lobate expansion of the side of the 

 tarsus. Attached to the articular membrane which unites the base 

 of the tarsus to the adjacent extremity of the segment that precedes 

 it (the protarsus) there are one or two pale but dark-tipped claw- 

 like spurs (the pedal spurs) *. In many cases there is a similar 

 spur (the tibia I spur) between the protarsus and the tibia. 



Fig. 6. Ventral surface of cephalothorax and of anterior end ol 

 abdomen of PakunncBiis. 



a., 1st abdominal sternum ( = sternutn of 3rd abdominal somite) ; b, respiratory 

 stigma ; c, trochanter of 4th leg ; d, coxa of 4th, e of 3rd, / of 2nd, 

 g of 1st leg ; h, maxillary lobe of 2nd leg ; i, maxillary lobe of 1st leg ; 

 k, pentagonal cephalothoracic sternum ; I, genital operculum ; m, seg- 

 mented shaft of pecten ; n, fulcra ; o, teeth of pecten. 



The abdomen is anteriorly as broad as the cephalothorax. It 

 .consists of twelve distinct somites, the last five of which are narrow, 

 tubular, flexibly jointed together, and constitute, with the post- 

 anal skeletal piece, the tail. This postanal skeletal piece consists 

 of two distinct parts an enlarged, usually globular basal portion 

 ( the vesicle), which contains a pair of poison-glands, and a spiniform 

 distal portion (the aculeus). Beneath the latter, on the vesicle, 

 there is frequently a tooth-like process, the vesicular spine. For 

 purposes of description and measurement, the vesicle and aculeus 

 are regarded as extended in the same straight line as the tail, the 



* These spurs must not be confounded with the thinner blacker spines most 

 frequently seen in their vicinity upon the extremity of the protarsus. 



