NOTES ON SOME AQUATIC OLIGOCHATA. 215 
EXPLANATION OF PLATES V, VI, and VII, 
Illustrating Dr. W. Blaxland Benham’s “ Notes on some 
Aquatic Oligocheta.” 
Heterocheta costata. 
Fig. 1.—The worm of the natural size. 
Fie. 2.—A specimen coiled, about twice natural size. 
Fie, 3.—Side view of worm, enlarged, showing the characteristic arrange- 
ment of chet. The segments are numbered and the annulations shown. 
Pr. Prostomium. JDors. Dorsal bundles. Vent. Ventral bundles,  Cten, 
Palmate cheete. 
Fic. 4.—One of the characteristic palmate cheetz from in front. 
Fig. 5.—The ‘‘ head” of a palmate cheta, more enlarged and in a different 
focus, showing now the apparently stronger outer prongs. 
Fic. 6.—A palmate cheta from the side, to show curvature of head. 
Fic. 7.—View of the free edge of a palmate cheta, showing curve, mem- 
brane, and ridges. 
Fic. 8.—A palmate cheta seen obliquely from above, to suggest Claparéde’s 
possible mistake in describing these chetz as ‘‘ cup-shaped.” 
Fic. 9.—An abnormal palmate cheta, with ridges feebly marked. 
¥ic. 10.—A furcate cheta from the dorsal bundle of Segment m1. 
Fig. 11.—A cheta from a dorsal bundle behind Segment xv. 
Fie. 12.—The free end of a furcate cheta from ventral bundle of Seg- 
ment Iv. 
Fie. 13.—The free end of a cheeta from a ventrai bundle of a more posterior 
segment to show the recurved proximal prong. 
Fic. 14.—The “head” of a furcate cheta from in front, the transverse 
ridge being the lower or proximal prong. 
Fie, 15.—An abnormal cheta, with two teeth between the chief prongs, 
from dorsal bundle of Segment xiv of a certain specimen. 
Fic. 15a.—The dorsal bundle of Segment xtv, showing the abnormal 
multidentate cheta (which is drawn too large, relative to the normal ones). 
Fie. 16.—Dorsal view of anterior end of a worm, showing abnormal arrange- 
ment of cheetse (see p. 194). 
Fig. 17.—A few segments of the worm viewed ventrally by transparency, 
