76. Clitellum extending to segment 19 or 20; male pores on segment 17 (an 



introduced genus) 



Dichogaster Beddard 



(Representative species, D. holaui (Mich.)) 

 Clitellum extending to segment 18; male pores on segment 19 

 Diplocardm Garman 



(Representative species, D. communis Garman) 



77. Gi2::ard vestigial or absent; southern species 78. 

 With one gizzard; western species 79. 



78. Calciferous glands in segment nine or in nine and ten; clitellum on seg' 



ments 13 to 19 or 20 (Family Ocnerodnlidae of some writers) 

 Ocnerodrilus Eisen 



(Representative species, O. occidentalis Eisen) 

 No calciferous glands; clitellum on segments 13 to 16 

 Microscolex Rosa em. Mich. 



(Representative species, M. phosphoreus (Duges)) 



79. (Two genera which are distinguished only by the minute structure of the 



nephridia or excretory organs) ; with '■'meganephridia" or one pair of 

 large nephridia in each segment 

 Plutellus E. Perrier 



(Representative species, P. marmoratus (Eisen)) 

 With '■'■micronephridia" or several pairs of small nephridia in each seg' 

 mcnt 



Megascolides McCoy 



(Representative species, M. americanus Smith) 



GENERAL REFERENCES 



Altman, L. C. 1936. Oligochaeta of Washington. Univ. of Wash. Pub. in 

 Biology, Vol. 4, No. 1, Seattle, Wash. 



Beddard, F. E. 1895. A Monograph of the Order Oligochaeta. Oxford. 



Bcnham, W. B. 1890. An Attempt to Classify the Earthworms. Quart. Jour. 

 Micros. Soc, Vol. 31. 



Cobb, N. A. 1918. Free-living Nematodes. Chap. 15 in Ward and Whip' 

 pie's 'Tresh'water Biology". John Wiley fe? Son. New York. 



Cobb, N. A. 1935. A Key to the Genera of Free-living Nemas. Proc. Hel' 

 minthological Soc. of Wash., Vol. 2, No. 1. Washington, D. C. 



Eaton, T. H. Jr. 1942. Earthworms of the Northeastern U. S. A Key, with 

 Distribution Records. J. Wash. Acad. Sci., Vol. 32. 



Eisen, G. 1900. Researches in the American Oligochaeta. Cal. Acad, of Sci., 

 third series Zool., Vol. 2, No. 2; Pp. 85-277. 



Galloway, T. W. 1911. The Common Fresh-water Oligochaeta of the United 

 States. Trans. Amer. Micros. Soc, Vol. 30, Pp. 285'^3 17. 



Gates, G. E. 1942. Check List and Bibliography of North American Earth- 

 worms. Amer. Midi. Nat., Vol. 27, Pp. 86-108. 



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