No.417.] NORTH-AMERICAN INVERTEBRATES. 737 
in four groups of three each, at about the level of the jaws. One 
B c V o n 67, Polyarthra platyptera Ehr. (Fig. 49) 
c3. Two very long spines (thrice the length of the body), attached 
ventro-laterally ; eyes two . . . . 68, Pedetes saltator Gosse 
cq. Three very long spines, two lateral, one ventral. Two eyes 
69, Triarthra longiseta Ehr. (Fig. 50) 
(The remainder of the group (a2) are less easily recogniza- 
ble. It will facilitate the use of the rest of the key to this 
subdivision to point out in a preliminary way certain striking 
characteristics of a number of species.) 
No eyes. — Hydatina senta (No. 87), Albertia (No. 63), Pleurotrocha 
(No. 91), 7 aphrocampa saundersia (?) (No. 92), Diglena contorta (No. 93). 
Eyes two.— Rhinops (No. 65), Diglena (Nos. 124-129), Distemma 
(No. 130, ZafArocampa saundersie (9) (No. 92), Triphylus (No. 8 5), 
Pedalion (No. 66), Pedetes (No. 68), Triarthra (No. 69). 
Eyes three. — Asplanchna priodonta (No. 74), Asplanchna herrickii 
(No. 73), TriophthaImus dorsualis (No. 122), Eosphora (No. 123). 
Parasitic. —. External, —Pleurotrocha parasitica (No. 91). Internal, — 
Albertia (No. 63), Hertwigia (No. 80), Proales wernecki (No. 110). 
Viviparous (the developing embryo frequently seen within the mother). — 
ier mam (No. 70), Asplanchna (Nos. 71-76), Rhinops vitrea 
(No. 65). 
No foot. — Trochosphera (No. 60), Pedalion (No. 66), Polyarthra 
(No. 67), Pedetes (No. 68), Triarthra (No. 69), Asplanchna (Nos. 71-76), 
Ascomorpha (Nos. 77-79), Hertwigia (No. 80), Anarthra (No. 8t). 
46. No anus, the intestine ending blindly 
cI. Foot present (viviparous) . . . . 
di. Foot small, on the ventral surface 
70, A. myrmeleo Ehr. (Fig. 51) 
Asplanchnopus 
c2. No foot : 
dr. Large, clear, sac-like animals, with incudate jaws (Fig. 54); 
corona with two slight conical elevations. Viviparous 
Asplanchna 
er. Saclike body with large projections or “ humps ” 
Jt. Four humps, — one dorsal, one ventral, and two lateral 
71, A. ebbesbornii Hudson (Fig. 52) 
J2. Three humps, — like the last but with the ventral one 
lacking (perhaps a variation of 71) — . 72, A. amphora 
Hudson 
«2. Sac-like body without humps 
Jt. Eyes three, — one large, on the brain, two small, lateral 
