32 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
rounding portions of the cuticle. These are densely massed together at the 
tip of the head, and a few isolated areolæ occur along the sides of the body 
near the head. Similar areolæ, but of larger size, are found also on the dorso- 
lateral surfaces of the tail lobes. The cuticle is elsewhere marked by minute 
intersecting lines, much as in the preceding species ; when studied in alcohol 
the cuticle appears to be areolated in its whole extent, but sections show that 
the apparent areole are nothing but slight elevations between the bundles of 
intersecting lines, the supposed areolæ themselves being striated by fine lines, 
Color, Remarkably iridescent. Whole body a light chocolate-brown color, 
the tip of the head the same. There is a dark ring immediately around the 
cloacal aperture. The whole surface of the posteloacal cuticular ridge is of a 
uniform brown color, without darker posterior edge, 
Dimensions. Length, 70 mm. ; greatest diameter, .5 mm. 
Comparison. This form resembles, but seems to be distinct from G. aquati- 
cus robustus. It differs from the latter as follows : in the presence of areolæ 
on the head and tail lobes; in the circumeloacal line of hairs ; in the uniform 
dark brown color of the posteloacal cuticular ridge ; in the absence of a 
dark ring around the neck, and of a white tip to the head. These characters 
seem to warrant placing it, preliminarily at least, as a new subspecies. 
3. G. lineatus Leidy. 
Figs. 20-31, Plate 4. 
G. lineatus Leidy, ’51. 
G. robustus Leidy, ’56. 
2G. seta Müll., Diesing, "61. 
G. lineatus Leidy, Villot, 74. 
G. aquaticus Linn., Römer, ’96. 
(Types: Leidy coll. 5008, Essex County, New York, 1851.) 
Form. Head end (Figs. 20, 21) rounded, not constricted from the body ; 
body cylindrical, somewhat narrowed anteriorly. Median grooves absent, 
Posterior end (Figs. 22, 23, 28) not swollen, obtusely truncated in the female. 
Males somewhat more slender than the female, and somewhat flattened. 
Tail lobes (Figs. 24-26) rather long and divergent, their distal ends curved 
inwards (ventrad). Cloacal opening elongate, above the lobes, Cuticular 
spicules of an elongate conical form on the median surfaces of the tail lobes, 
though not on the distal ends of the lobes. Two rows of rather long branch- 
ing hairs on the ventral surface of the body; one row on each side of the 
median line, each row extending from a little in front of the cloacal opening to 
a little behind the point of bifurcation of the tail lobes ; the hairs are longest 
in the middle of each line, Tail lobes concave on their medio-ventral surfaces. 
Cuticle (Figs. 29-31). Areolated, areolæ closely opposed without inter- 
vening spaces ; rectangular or polygonal in outline, frequently elongated in 
the direction of the body axis, and with a tendency to group themselves into 
