* Eustrongylides Jägerskiöld, 1909

Generic diagnosis (after Measures 1988b). Dioctophymatidae. Encapsulated L3 and L4 occur on mesenteries of fish hosts, including pumpkinseed Lepomis gibbosus, rock bass Ambloplites rupestris, and yellow perch Perca flavescens. L3 retain 2nd stage cuticle. Two circles of labial papillae surround mouth. Six papillae of the inner circle single with narrow bases and spike-like apices. Six papillae of outer circle have broad bases and nipple-like apices. In males the spicule primordium enters rectum dorsally (Fig. 16 A); genital primordium enters ventrally, and extends anteriad almost to oesophago-intestinal valve where it curves posteriad and terminates bluntly. Caudal sucker of males more developed in L4 than in L3. In females, genital primordium extends anteriad (Fig. 16 B), and curves posteriad, with its blunt extremity ending behind intestine-rectal junction. For length and width of male and female L3 see key above. L4 retain 2nd and 3rd stage cuticles. Labial papillae of L4 similar in shape and position to those of L3 but larger and more prominent (Fig. 16 C). Male and female genital primordia include thin-walled hologonic testis and ovary respectively. For length and width of male and female L4 see key above. One species, * E. tubifex, has been found as L3 and L 4 in various Canadian fresh-water fishes. Adult E. tubifex occur in the proventriculus of mergansers and other piscivorous birds.