SEA-FISHERIES LABORATORY. 458 



distal portions by a transverse suture. At the distal end 

 the seta is either perforated or the membranous covering 

 is extremely thin. The olfactory setae differ from the 

 tactile setae in having numerous nerve elements for each 

 seta. They are present on the exopodite of the antennule 

 on the side opposite to the long setae. They are extremely 

 small, and there are only one or two on each ring of the 

 exopodite. On the endopodite of the antennule there are 

 also a few small setae on the dorsal side of each ring, 

 which have the appearance of olfactory setae. The 

 gustatory setae present in the region of the mouth are 

 modified olfactory setae. 



REPRODUCTIVE ORGANS 



(Plate XII). 



1. Male (fig. 78). 



The abdomen is much narrower than in the female, 

 and the third, fourth and fifth abdominal somites are 

 fused together. Abdominal appendages are present only 

 on the first and second abdominal somites, and these are 

 modified to form copulatory organs. The external genital 

 apertures are paired^ and each is situated at the tip of a 

 membranous papilla on the ventral side of the coxopodite 

 of the last walking leg. The thoracic sterna are deeply 

 concave, in order to receive the closely-applied abdomen. 

 The locking apparatus of the male abdomen is much 

 better developed than in the female. The dorsal side of 

 the carapace is much flatter in the male than in the female. 

 As Williamson has pointed out, the lobed antero-lateral 

 border of the carapace is slightly turned up in mature 

 males. The chela of the mature male are larger than 

 those of mature females of the same size. 



The two abdominal appendages of each side form a 



