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CALIFORNIA ACADEMY OF SCIENCES. 



same. In Menopon and Colpocephaluni the anterior pro- 

 cesses of the sclerite are very much prolonged forward 

 and are only slightly divergent. In some cases the 

 sclerite is extremely reduced in size. In Menopon foedus 

 the anterior processes are not prolonged but are v\'ide 

 and bifid. These two genera are in other respects also 

 very similar, and it is of significance that in the only 

 genera of the Amblycera that possess the sclerite it has 

 the same structure, different from that prevailing 

 amongst the Ischnoceran genera, in each. 



The following table gives the species of Menopon 

 examined that have and do not have the sclerite and 

 glands: 



