ON THE STRUCTURE OF BIMASTOS PALUSTRIS, 

 A NEW OLIGOCHAETE. 



H. F. MOORE. 

 (School of Biology, University of Pennsylvania.) 



The earthworm of which this paper treats is not uncommon 

 in the vicinity of Philadelphia, where it was first discovered in 

 Fairmount Park, in February, 1893. 



Since then it has been found in a number of places in Penn- 

 sylvania and New Jersey, within thirty miles of its original 

 locality, and it will probably be found to extend, at least, 

 throughout the valley of the Delaware River system. 



It frequents the damp, soft soil on the banks of springs and 

 streams, but has not been found in the bottom mud. It has 

 been taken in common with Allurus tetraedrus, Sperganophilus 

 tamesis, and several species of Lumbricus and Allolobophora. 

 I have not found its cocoons, and the only fact that I have 

 learned, relating to its breeding habits, is that individuals bear- 

 ing spermatophores are found from the latter part of February 

 until the first of December, when this is written. 



The anatomy has been studied by means of dissections, sup- 

 plemented with continuous series of longitudinal and transverse 

 sections. 



External appearance. — This worm may reach a length of 

 three inches when fully extended, the number of somites vary- 

 ing from eighty to one hundred. The anterior somites are 

 somewhat longer than those behind the clitellum, but the 

 disparity is not so marked as in many other terrestrial Oli- 

 gochaeta. 



The prostomium is large and not distinctly dovetailed into 

 the peristomial somite, being continued upon the latter by a 

 pair of grooves which traverse about one-half of its length, and 

 are not connected posteriorly by a transverse groove, as in 

 Allolobophora and species of Lumbricus. 



