456 Illinois State Laboratory of Natural History. 



The relation of the species under consideration to other 

 Tubificidce cannot be finally determined in the light of our 

 present knowledge of the anatomy of this species and of 

 nearly related forms. In the presence of prominent non-re- 

 tractile papillae it resembles Peloscolex, Spirosperma, Hemi- 

 titb'ifex, and Embolocephalus. It probably is closely allied to 

 Leidy's Peloscolex variegatus ('52, p. 124), but the meager 

 description of that form and the lack of type specimens make 

 it impossible to determine this point. The absence of a chiti- 

 nous sheath about the penis distinguishes it from Spirosperma 

 and Hemitubifex, but there are no characters given in the 

 description of Embolocephalus Randolph ('93, p. 472), which 

 exclude it from that genus. The description includes, however, 

 no account of the circulatory system in the anterior part of 

 the worm nor any statement as to the presence or absence of a 

 chitinous penis sheath. Sections of E. plicatus kindly sent 

 me by Dr. Randolph furnish no evidence of the presence of 

 this sheath in that species, but as they include none of the first 

 eight somites it is impossible to compare the anatomy of the 

 circulatory systems of the two species in that region. In 

 view of the above facts I have included the Illinois species in 

 the genus Embolocephalus, giving it the species name multi- 

 setosus. It differs from E. velutinus in having two kinds of 

 dorsal seta?; and from E. plicatus in having palmate seta? 

 in the dorsal bundles, and in other particulars as follows : 

 (1) In plicatus the dorsal bundles are said to contain usually 

 but six capilliform seta? and three uncinate ones, and no state- 

 ment is made to indicate that there is any considerable vari- 

 ability in the number in different regions of the body. In 

 multisetosus, however, the dorsal bundles of the anterior region 

 each contain from eight to sixteen seta j , while in the middle of 

 the body the number is much smaller, and the posterior somites 

 usually have no dorsal seta? whatever. (2) The papilla? of 

 plicatus are in two rows, equally distant from the septa, while in 

 multisetosus one row is in the plane of the seta j and the other in 

 the plane of the septa. The papilla? of multisetosus are also 

 much larger and more conspicuous than those of plicatus. 

 (3) The diameter of the lumen of the sperm-duct of plicatus is 

 nearly uniform throughout, while that of multisetosus is several 

 times greater in the region of the atrium than elsewhere. 

 Urbana, 111., Jan. 25, 1900. 



