MONTGOMERY: GORDIACEA. 35 
¢, 45) is of slightly greater diameter than the part of the body immediately 
preceding, tip of the head rounded or truncated; in one specimen a groove on 
the ventral surface of the head. Body either flattened or cylindrical, with 
deep dorsal and ventral median grooves. In all females except one the pos- 
terior end (Figs. 42 a, 48, 44) of the body is somewhat constricted for a dis- 
tance of about 6 mm., but the extreme posterior end is usually swollen, some- 
what knob-shaped ; on lateral view this end appears obliquely truncated, the 
posterior end of the body has a vertical groove on its terminal aspect, and the 
cloacal aperture is not exactly terminal, but somewhat ventral. 
In the male the anterior portion (Fig. 40) of the body is not attenuated, 
though it is slightly flattened horizontally; the head is elongate-oval in out- 
line, of greater diameter than the part immediately preceding, and is terminally 
rounded. The body like that of the female, but more slender. Tail lobes 
(Fig. 41) rather slender and long, asymmetrical, their distal ends curved 
ventro-mediad ; they are nearly cylindrical, flattened only on the median sur- 
face. The large, elongate cloacal aperture is situated on the ventral surface of 
the body, and separated from the anterior point of bifurcation of the tail lobes 
by a distance equal to half the length of the tail lobes. This aperture does not 
lie in a groove ; nor do spicules nor long hairs occur near it or on the tail lobes, 
but only minute, short hairs. 
Cuticle (Figs. 46-49). Areolated ; the areole slightly smaller than those 
of G. densarcolatus, more or less of the same size, and either irregularly 
polygonal or somewhat elongate in outline, and then usually elongated in the 
direction of the transverse axis of the body. The areole are usually well 
separated from one another, except in the median line, and show no tendency 
to produce confluent rows. Small interareolar groups of small bristles oecur 
in most of the individuals, these bristles varying in number and form. 
Color. Brown, varying in shade, but never very intense ; tip of head lighter, 
and a more or less pronounced dark ring around the neck. In the male an 
obscure brown ring immediately surrounds the cloacal aperture. 
Dimensions. Length of male, 216 mm.; greatest diameter, 1mm. Length 
of largest female, 335 mm.; greatest diameter, 1.4 mm. 
Comparison. In the configuration of the cuticle this species is most closely 
allied to G. violaceus Baird, and to G. densareolatus mihi. The males of these 
three species are very different, however, in regard to the arrangement of the 
spicules on the posterior end, such spicules being absent in platycephalus. 
This character does not serve to distinguish the females of these species how- 
ever, though the flattening of the anterior portion of the body is diagnostic of 
platycephalus. But I am wholly at a loss to classify one female from Montana 
in the collection of the Acad. Nat. Sci.: it has the flattened head of platyceph- 
alus, with the confluent areole of densareolatus ; its color is a deep buff, with a 
narrow black ring immediately around the mouth, but with no dark ring 
around the neck; the shape of the posterior end and the deep median grooves 
of the body resemble platycephalus, so that on the whole I should be inclined 
to consider it as platycephalus. But might not this specimen be a hybrid be- 
