110 THE FAMILY OP THE DRSMACIDIN'AE. 



Desmacklon and Afij.rilla on one side, and between the genera 

 Esperia and Desmacidon on the other side, are the cause 

 that the systematic arrangement of these genera presents 

 considerable difficulties. Between the two former, as well 

 as between the two latter we observe gradual transitions. 

 There are plenty of species that can be arranged under 

 either of the two genera. So for instance it may be either £5- 

 peria ancpps 0. S. or Desmacidon anceps 0. S. In the 

 „Zweite Deutsche Nordpolarfahrt" l) Schmidt says: „Ich 

 habe in meinen letzten Arbeiten die proteusartige Gattung 

 Des^man.dov einigermaassen zu begrenzen versucht, jedoch 

 mit dem Zugestiindniss , dass sie nur ganz kiinstlich gegen 

 die jiltere Gattung Esperia abgespert werden kann." Even 

 the characteristic Esperia-anchors are not always a good 

 criterion for the difference between the two genera. Des- 

 macidon anceps 0. S. '74 is however not the only example. 

 We have further Esperia lanugo 0. S. '75, Esperia tituhans 

 0. S. '70. Rhaphiodesma Parishii Bwk. '75 and many 

 others which show a considerable instability in the form 

 of their anchors. Nor is the difference between Desmaci- 

 don and ^fy.villa a distinct one. Schmidt himself says of 

 his Desmacidon caducum that it may either be placed un- 

 der Myxilla or under Desmacidon. 



Although , there are numerous transitions from Esperia 

 to Desmacidon, and from this to J^fiixilla, nevertheless it 

 is easy enough to distinguish the true Desmacidon s from the 

 true Esperia" s or MyxUWs. So , having the choice either of 

 uniting all these forms in one very large genus showing gra- 

 dual transitions between the extremes , or of retaining generic 

 subdivisions,. I think it to be advisable, from a simply 

 practical point of view , to briug , the indisputahle forms 

 under one of these three genera, and the others to Am- 

 philectus 2) nov. gen. I consider this genus Ampliilectus 



1) Pag. 430. 



2) «ix<pf/,SKTOi; , diiliious. 



Notes irom Ihe Leyclen IMiiseuni, "\''ol. II. 



