340 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



b. No conical spicules behind the cloacal aperture. 



G. platycephalus Montg., i . 

 III. Posterior end not lobed, spirally inrolled, with a depression or 

 groove on its ventral surface, narrower than preceding portion 

 of body (Chordodes, 6 6 ). 



A. Cuticular areoles longer than high, on and between them small 



circular pits Chordodes occidentalis Montg., $ . 



B. Cuticular areoles higher than long. 



a. Spines on the summits of the highest papillae. 



C. pueriiis Montg., i. 



b. No spines on the summits of the highest papillae. 



C. morgani Montg., 6 . 

 TV. Posterior end not lobed, not spirally inrolled. 



A. Posterior end not noticeably enlarged (Gordius, 9 2 ). 



a. With elevated cuticular areoles on the whole surface of the 



body. 



1. With paired dark stripes in the median lines. 



Gordius leidyi Montg., 2 . 



2. No dark stripes in the median lines. 



a. Areoles elongated in the long axis of the body, well 



separated G. longareolatus Montg., 2 . 



b. Areoles not elongated in the long axis of the body. 



1. Areoles closely apposed, tending to produce 



longitudinal ridges G. lineatus Leidy, ? . 



2. Areoles more or less confluent, tending to pro- 



duce transverse rows, head usually cylin- 

 drical G. densareolatus Montg., 2 . 



3. Areoles usually separated, interareolar groups 



of fine hairs, head usually flattened. 



G. platycephalns Montg., 2- 



b. Without elevated cuticular areoles on the whole surface of the 



body. 



1. No cuticular areoles. 



a. Cuticle dotted with white spots. . G. aquaticus Linn., 9. 



b. Cuticle without white spots. ..G.a. robitslus (Leidy), 9 . 



2. Cuticular areoles at the ends of the body only. 



G. a. difficilis Montg., 5 . 



B. Posterior end swollen, somewhat knob-shaped, sligbtiy con- 



stricted off (Chordodes, 9 9). 



a. Cuticular areoles longer than high, on and between them 



small circular pits Chordodes occidentalis, Montg. , 2 • 



b. Cuticular areoles higher than long. 



1 . Spines on the summits of the highest areoles. 



C. pueriiis Montg., 9 • 



2. No spines on the summits of the highest areoles. 



C. morgani Montg., 9. 



Wistar Institute of Anatomy, 



Philadelphia, Pennsylvania., 

 June 20, 1898. 



