DESCRIPTIONS OF A NEW GENUS AND SPECIES OF THE 



DISCODRILID WORMS. 



By Maurice C. Hall, 



Assistant Zoologist, United States Bureau of Animal Industry. 



Some worms collected on crayfish in the creeks of the Great Basin 

 near Salt Lake City, Utah, by Mr. George Haley, were sent in to the 

 zoological division of this bureau in December, 1913, and were found 

 by the writer to be discodrilids. A comparison with the forms 

 given in Pierantoni's (1912) valuable monograph and with the new 

 species added by Ellis (1912) showed that the Utah specimens con- 

 stitute a new genus and species. The writer is indebted to Prof. 

 J. Percy Moore, of the University of Pennsylvania, for assistance in 

 connection with the literature dealing with this group of annelids. 



According to Pierantoni (1912) the discodrilids constitute a quite 

 homogeneous group of modified oligochaetes, ranging in size from 

 1 mm. to 12 mm. long, with a maximum width, when in a state of 

 moderate distension, not to exceed one-tenth of the body length. 

 According to Pierantoni the maximum width is attained in the 

 posterior third of the body, the ends always being narrower, but 

 Ellis (1912) lists Cambarincola pMladelpMca as having the head as 

 wide as or wider than the greatest body width. 



There is a distinct oval or cylindrical cephalic region, with a more 

 or less profound median sulcus. The mouth is surrounded by a 

 fleshy ring, sometimes divided into two or more equal or unequal 

 lobes which may be prolonged into digitiform or tentaculiform ap- 

 pendages. Inside of the mouth, at the base of this fleshy ring or 

 sucker is a circlet of numerous minute papillae. The median sulcus 

 is at the base of the circumoral sucker. The cephalic region is divis- 

 ible into 3 segments, the praestomium and 2 succeeding segments, 

 the third very small. The first extends to the median sulcus. The 

 division is based on the structure of the nervous and circulatory 

 systems in this region. 



The trunk region always consists of 11 segments, of which 8 are 

 quite distinct, the last 3 being small and rather indistinct. The last 

 segment is prolonged into a terminal sucker. The 8 prominent 

 anterior segments are constantly divided into 2 unequal parts by a 

 sulcus toward the posterior fourth of the segment. The region im- 

 mediately following the cephalic is somewhat narrower than the 

 cephalic in all species. The fifth, sixth, and seventh segments are 



Proceedings U. S. National Museum, Vol. 48— No. 2071. 



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