Oligochaeta Collected by the Canadian Arctic Expedition 



1913-18. 



By FRANK SMITH and PAUL S. WELCH. 

 (With three figures in text.) 



An opportunity to examine the collections of Oligochaeta made in the 

 Arctic regions of North America by the Canadian Arctic Expedition has been 

 very welcome, since it has made it possible to materially extend our knowledge 

 of the oligochaete fauna of the Arctic zone as well as that of North America. 



The Lumbriculidae and Enchytraeidae are the only families represented, 

 and are the ones which our knowledge of their distribution in the Arctic regions 

 of Eurasia would lead us to expect. A general similarity is found between 

 the oligochaete faunas of the two regions, although they are not identical. 



The Lumbriculidae in the collections have been studied and are here dealt 

 with by the senior author, while the part dealing with the Enchytraeidae and 

 including the descriptions of the new species is by the junior author. The 

 collections which are from quite a wide range of localities and a considerable 

 variety of habitats were made by Mr. F. Johansen, the marine biologist, ento- 

 mologist, and botanist of the expedition. 



It is interesting to learn from the field notes of the collector, that some of 

 these worm's were found alive in dried-out creek beds and pond bottoms where 

 they had taken refuge in moss or other vegetation. Others were found unharmed 

 by exposure to freezing conditions. In these respects they resemble some of 

 their relatives of more temperate regions. 



I. THE LUMBRICULIDAE 1 

 BY FRANK SMITH. 



This family is represented by the single genus Lumbriculus, and there are 

 but two species. L. variegatus (Miiller), the well-known Eurasian species is 

 the more abundant and widely distributed form, and L. inconstans (Smith), was 

 found associated with it in two localities. 



Lumbriculus Grube. 



Prostomium rounded, without proboscis-like elongation. Setae paired and 

 cleft. Spermiducal pores one or two, exceptionally three; paired or asymmetric- 

 ally placed on one or two somites, more commonly on 8 2 or 10. Oviducal 

 pores usually paired in one or two somites next following those with spermiducal 

 pores, sometimes otherwise arranged. Spermathecal pores laterad of ventral 

 setae; usually in three to five pairs, frequently fewer or more numerous, often 

 asymmetrically arranged; commonly posterior to spermiducal pores. Dorsal 

 and ventral vessels connected in posterior part of each of nearly all somites by 

 a pair of transverse vessels; dorsal vessel in anterior part of each somite, except 

 a few anterior ones, with one pair of contractile caecal transverse appendages. 

 Atria, one, two, or three; paired, or asymmetrically arranged in one or two 



iContributions from the Zoological Laboratory of the University of Illinois, No. 139. 

 2 Arabic numerals are used to designate somites, counting from the anterior end. 



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