CASTLE: NORTH AMERICAN RHYNCHOBDELLIDA. 55 
in Figure 6, Plate 2. They include five longitudinal rows of papille found on 
the middle (sensory) annuli of usually all the triannulate somites. These rows 
may be designated, from their position, median, marginal, and intermediate, the 
first named being unpaired, the other two paired. 
A row of papille is found also between the median and each intermediate 
row, but these papille are situated not on the middle, but on the posterior 
annulus of each of the somites from about yu. to xxi. inclusive (Figure 6). 
These will be designated paramedian rows. 
The most conspicuous papille of somites xxv.-xxvir. are usually placed as 
indicated in Figure 6. They consist, first, of a continuation of the marginal 
rows back to the anus; secondly, of two rows of three papillae each, placed one 
on either side of the median plane and too near it to fall in the paramedian 
rows found farther forward. 
Other less conspicuous papille occur on the dorsal surface of the body and 
posterior sucker, but no papille are found on the ventral surface of the 
animal. 
The general color of the body above is brown variegated with yellow, orange, 
and green. Light areas of yellow or pale orange form : — 
I. A median vitta extending from the anterior end of the body back to somite 
xxv., usually without interruption, but not always so, and expanding commonly 
at six places, namely, (1) in somites vi. and vi. (Figure 32, Plate 8) ; (2) in 
somite 1X.; (3) in somites xu. and xmt.; (4) in somites xy. and xvr.; and 
(6) in somite xxi. (and the posterior part of somite xx1.). The median row 
of papillae already described falls entirely in the median light vitta. In somites 
XXV.-xxvil. both vitta and papillz become double, dark pigment being found 
along the median line back to the anus, usually behind it also quite to the 
posterior margin of the acetabulum. The double (or paramedian) light vitta 
of somites XXV.-XXVII. contains the three pairs of papille shown in Figure 6, 
Plate 2 ; it may or may not be continuous with the median light vitta farther 
forward. 
II. Throughout the greater part of the body the papille of the intermediate 
rows lie each in an irregularly rounded light spot. The successive spots of 
each half of the body may become confluent so as to form an irregular, 
frequently interrupted, longitudinal band. 
III. The margins of the body are conspicuously marked with metameric 
light spots from about the third or fourth somite back to somite xxv. Some 
idea of the form and position of these spots may be obtained from an examina- 
tion of the stippled areas in Figure 6, Plate 2, and Figure 32, Plate 8. Each 
spot is typically V- or U-shaped and is placed on the adjacent non-sensory rings 
of two successive somites. The usually hollow centre of the V or U is formed 
by a spot of brown sometimes bordered with orange. The margin of the sen- 
sory ring is generally darker in color than its more median parts, so that it is 
strongly in contrast with the metameric light spots which it separates. 
The posterior sucker is decorated with radially placed triangular light spots 
(Figure 6) resembling the marginal spots of the body. Other irregularly 
