MONTGOMERY: GORDIACEA. eA 
Color. Variable according to age, and apparently also according to locality. 
The body varies from a yellowish white to a yellowish brown, or a light 
chocolate-brown ; the males are usually darker than the females, The tip of 
the head is white, and behind it a broad reddish brown ring is to be seen in 
most specimens (not present in some females from Kansas). In all the females 
a more or less intense reddish brown ring immediately encircles the cloacal 
aperture ; and in some specimens there is a narrower, lighter ring outside of 
and separated from the former. In the male a similar dark ring encircles the 
cloacal opening, at a little distance from it ; and a spot of deep brown may lie 
at the posterior edge of this ring : the postcloacal cuticular ridge is brown, its 
posterior edge a much darker reddish brown. 
Dimensions. Largest male, 655 mm. ; greatest diameter, 1.3mm. Largest 
female, length 705 mm.; greatest diameter, 1.9 mm. The males are more 
slender and usually somewhat shorter than the females. The individuals from 
the western United States (Montana, Kansas) averaged considerably longer 
than any eastern specimens examined. 
Comparison. This species has been placed by me as a subspecies of G. aqua- 
ticus Linn., since the differences do not warrant ranking it as a separate species. 
It differs from the true European aquaticus in these points : the presence of a 
dark ring around the female cloacal aperture, the absence of a row of hairs 
around the male cloacal aperture, and the absence of white spots (“ helle 
Flecken”) on the cuticle. 
Especial Diagnostic Characters. The approximately equal diameter of the 
whole body, with the obtuse truncation of the two ends; the absence of true 
areoles, and the presence of short hairs on the cuticle ; the presence of a trans- 
verse postcloacal cuticular ridge in the male, the posterior edge of which is 
darkest in color, and the absence of a line of hairs around the cloacal aperture. 
Geographical Distribution. Ihave seen specimens from Maryland, Massachu- 
setts, District of Columbia, New York, Maine, Pennsylvania, Montana, and 
Kansas ; and Leidy mentions its occurrence at the Bay of Fundy. The speci- 
mens of “ G. aquaticus” mentioned by Romer (’95), from South America, are 
probably specimens of our subspecies. 
2. G. aquaticus difficilis, n. subsp. 
Figs. 14, 15, Plate 3. 
(Type: 1 male, Leidy coll. 5100, Roan Mt., N. Carolina.) 
Form. General form as in the preceding subspecies, cylindrical with the 
greatest diameter posteriorly, head (Fig. 14) rounded. Posterior end (Fig. 15) 
as in the preceding, but a parabolic line of hairs curves around the cloacal 
aperture, the posterior ends of this line of hairs situated upon the latero-ventral 
surfaces of the tail lobes, at about the plane of anterior bifurcation of the 
latter. 
Cuticle. At the tip of the head there are small, round or polygonal promi- 
nences or areol, of slight elevation, and of a deeper brown color than the sur- 
