1904.] NATURAL SCIENCES OF PHILADELPHIA. 805 



Though present in all but one, the clitcllum is perfect!}^ developed 

 only in the largest specimen. It covers seven segments, XIII to XIX 

 inclusive, and is completely annular and of uniform thickness on the 

 first five, but interrupted or much thinner on the middle ventral region 

 of the last two. On the posterior clitellial and several of the immedi- 

 ately succeeding segments occur certain papillae and grooves utilized 

 during copulation. Two pairs of papillse, situated on the posterior 

 part of XVII or on -^^ and on the posterior part of XX or -f ^, are 

 constant on all of the specimens ; a third pair situated on XXI or ^j^^^ 

 is complete in one specimen, represented by a median papilla in one, 

 by the left only in three specimens, by the right only in one, and is 

 totally absent in the seventh, in which, however, indistinct thickened 

 areas appear in the median field of ™j and ^gj\. In one specimen a 

 small median papilla is present on XVII between those of the pair. 

 When the papillse overlap the contiguous iDorders of two segments, 

 which is the normal condition, the affected furrows are obliterated 

 ventrally. In most cases the first pair of papillae are much the largest 

 and the third the smallest, but in this respect also they are variable. 

 All of the papillffi are low, broad disks of an irregular elliptical or some- 

 times circular form. The central portion is more translucent and 

 either elevated or depressed above the more opaque, firmer rim which 

 contains a circle of glands. The entire structure of these papillse 

 indicates that in addition to a secretory adhesive function of the rim 

 the center acts as a true vacuum sucker. Just anterior and posterior 

 to each pair of suckers transverse grooves usually extend across the 

 venter and other shorter and less constant ones may occur. Very con- 

 stant and conspicuous are a pair of longitudinal grooves reaching in the 

 line of the ventral seta from the middle of XVIII to the middle of XX. 

 Each groove consists of three parts: a short anterior section reaching 

 from the setaj of XVIII to the furrow ^x^x^, a longer middle section 

 extending for the entire length of XIX, and a short posterior section 

 completing the groove to the setae of XX. All three sections are 

 strongly curved, the anterior and posterior with the convexity outward., 

 the middle with the convexity directed inward. At the point of junc- 

 tion of the anterior and middle sections, in the furrow ^xix"' ^'^^' g^'oo'^'^ 

 enlarges into a small triangular sinus containing a minute papilla upon 

 which the male pore opens. This is perhaps situated rather more on 

 XIX than XVIII. At each end of the groove and just external to the 

 closely approximated penial setse of somites XVIII and XX are the 

 external openings of the two pairs of prostate glands, the secretion of 

 which is therefore brought to the sperm by means of this groove. Tl.c 



