Myria'poda of West Africa. 35 



the mentum and hypostoma. It is not impossible that these clifFer- 

 ences are sexual, but on this point no information is available. 



We are aware that these three species of Spirostreptus do not 

 differ by any very important characters from many previously pub- 

 lished descriptions, though they do not appear to be entirely in 

 accord with any. A large part of the older descriptions consist 

 chiefly of accounts of the colors of alcoholic or dried specimens, in 

 which the colors depend on the strength of the alcohol, the rapidity 

 of the drying process, or the age of the specimens, as we have 

 frequently observed in collecting species of this family. There are 

 numerous descriptions which do not give a single morphological 

 character not present, in all probability, in every Spirostreptus, and 

 it appears to us that to describe these specimens as new will be 

 likely to cause less confusion than to make a random reference of 

 them to species practically undescribed, our species being character- 

 ized, we hope, with suflScient completeness to make their identifi- 

 cation possible to any one studying the older types. In the other 

 case such study would be quite as likely to prove the distinctness 

 of the forms before us, and to cause complications in the literature 

 of the subject much greater than the simple reduction of our specific 

 names to synonyms. 



We are also aware that many of the characters mentioned by us 

 could probably be relegated to a properly prepared generic descrip- 

 tion, had such been drawn up. 



The distinctions between Spirostreptus and allied genera are by 

 no means settled. Latzel puts forward the number of pectinate 

 lamellae as an important generic character, and states that Allo- 

 porus has eight, and Spirostreptus nine or ten. We have found 

 eleven to be the constant number in the specimens referred to these 

 genera, but sometimes the rows are more or less incomplete, so 

 that variation in the number appears probable, and hence the only 

 remaining distinction between the two genera is the possession by 

 Alloporus of repugnatorial pores on the fifth segment, and the im- 

 portance of this character is more or less weakened by the fact that 

 on specimens of Spirostreptus, rudimentary pores, in the shape of 

 small depressions, sometimes occur on the fifth, fourth, and third 

 segments. 



