DESCRIPTIONS OF TWO NEW LEECHES FROM PORTO RICO. 
217 
becoming a dull orange on the ventral surface, where it forms a continuous uniform area occupying 
about two-thirds of the width of the body and entirely uninterrupted by any markings. At the sides 
this area is. delimited bya pair of sharply contrasting broad bands of dull black, in the borders of 
which are scattered some irregular spots of deeper black. External to the black bands, and marking 
the exact margins of the body, are two narrower bands of the ground color, but somewhat paler than 
the ventral surface. The dorsal color pattern produces a very beautiful effect. Briefly stated, it consists 
of five dark longitudinal bands, separated by four of the ground color, which also appears more or less 
within the dark bands. Of the five latter the unpaired one is the widest and is divided along the 
median line into halves by a regularly broken line of vivid black, which is flanked at intermetameric 
intervals by pairs of black spots. A pair of narrower supramarginal bands bear upon their outer 
flanks regularly arranged outstanding black spots, between which and the yellow marginal stripes the 
ground color becomes of a nearly pure olive. The intermediate bands, or second pair, are still narrower 
and are situated about midway between the median and supramarginal bands. 
Inasmuch as the color pattern of this species throws much light on the character of the segmenta- 
tion of the body a further description, especially of its metameric features, is now given. When fur- 
ther analyzed each of the dark bands is seen to be composite, being constituted of longitudinal elements 
or narrower lines, which are the result of the greater or less admixture of black pigment with the 
ground color. In general the dark pigment is more dense along the margins of the bands, resulting in 
the formation of narrow black borders to sooty or clouded olive stripes. The bands are further made 
up of serial units, the metameric and intermetameric distribution of which is expressed in each by an 
evident tendency to widen in the middle and to shrink or even become suppressed at the ends of 
somites. Each band consists, therefore, of a series of metameric enlargements, alternating with con- 
strictions, which are here termed intermetameric because they extend over the contiguous portions of 
two adjacent somites (as somites are determined in this paper). In complete and typical somites the 
metameric elements belong to the three middle annuli (62, «2, and 65), while the intermetameric 
are confined to the first and fifth (61 and 66) ; but in the entire series the last annulus of one somite 
is united with the first of the succeeding somite in respect to color effectiveness (pi. 12, fig. 4). 
The metameric elements (fig. 4) are found: (1) In both borders of the middle and intermediate 
bands and the ental border of the lateral, all of which become much more sharply defined or of a 
deeper black in the three middle annuli and more diffuse and obscure or entirely suppressed on the 
terminal annuli. (2) In the median black line, which, as above noted, is not continuous, but formed 
of a. series of short black dashes, each of which is a bold distinct stroke extending over the three 
middle annuli and interrupted by light areas on the first annulus and the fifth. Usually there is no 
blending of successive dashes, but sometimes the intervening areas become more or less suffused with 
black pigment, which is more likely to occur on the first than on the fifth annulus. (3) In the 
black spots which lie on the outer borders of the lateral bands. These are of a deep black color and 
occur constantly on the second (62) and fourth (65) annuli, respectively anterior and posterior to 
the dorso-marginal sensillpe, around the internal side of which they are connected by a delicate arch 
of black pigment. To these positive elements may be added some negative elements: the light spots of 
more or less pure ground color which are included within the widened portions of all the bands, viz., 
a pair flanking each segment of the median black line of the unpaired band, a series of similar spots in 
each of the intermediate bands, and less distinct ones in corresponding positions in the lateral bands. 
The intermetameric elements (pi. 12, fig. 4) of the lateral and intermediate bands are the lather 
negative features of the contracted regions on the first and fifth annuli. Here the black borders lose 
their intensity, and the black pigment becomes diffused and distributed almost uniformly across the 
whole width of the bands, thus separating from one another the light serial spots above mentioned. 
In the corresponding parts of the median band the black pigment becomes largely concentrated into a 
pair of intense spots, extending over the fifth (66) and first (61) annuli, and including between them 
a more or less clear light spot, the repetition of which causes the series of breaks in the median black 
line above mentioned. 
On the incomplete somites at the anterior end all of these markings may be distinguished, and 
as they retain their exact relative positions they afford an important clue to" the homology of the 
developed annuli. All five of the bands become more distinctly constricted intersegmentally, the 
intermediate pair finally breaking into two series of elliptical spots and the lateral similarly into 
series of crescents, the horns of which embrace the dorso-marginal sensitise. On somite viri, in which 
the annuli 61 and 62 are incompletely developed, the median black dash extends over a'2, 65 and the 
