Tironella gen. nov.

Diagnosis. Tironin synopiids with dorsal and anterior margins of head in lateral view set at right angle, front rounded; eyes present, accessory eyes verified only in Tironella altifrons . Interantennal head margin rounded or straight with angular lower corner. With mandible palp, palp article 2 straight. Coxal plates 1–3 of subsimilar shape, successively longer, plate 4 about half as long as 3 with concave posterior margin, plates 5 and 6 strongly posterolobate, combined as broad as first 4 plates, plate 7 wider than deep. Gnathopod 1 and 2 basis straight, carpus slender, elongate, about as long as basis, dactylus with unguis nearly straight, about half as long as propodus; propodus of gnathopod 1 with posterior row of pectinate setae. Pereopods 3–7 dactylus with unguis short and curved (prestubby) with stout curved robust seta countering unguis (Fig 5 dac, P dac). Uropods 1 and 2 reaching just beyond apex of peduncle of uropod 3, uropod 3 outer ramus of single article.

Etymology. Named after the type-genus with the diminutive-ending – ella added to it.

Type species. Tironella bathyalis sp. nov. — Here designated.

Component species. Tironella altifrons (Reid, 1951) comb. nov.; T. bathyalis sp. nov.; T. pervicax (J.L. Barnard, 1967) comb. nov.

Distribution. South Eastern Australia, Pacific Mexico, West Africa.

Key to species of Tironella gen. nov.

1. Interantennal lobes broadly rounded; uropod 3 outer ramus with 4 robust setae dorsally. telson “each of its halves has three groups of dorsal bristles [Reid 1951]”................................................... T. altifrons (Reid, 1951)

- Interantennal lobes bluntly right angled; outer ramus of uropod 3 with about 6 to 9 robust setae dorsally; telson with 4-8 small robust setae in row dorsally on each lobe................................................................... 2

2. Gnathopod 1 basis anterior margin with row of long strongly plumose setae; pereopods 3 and 4 dactylus curved, moderately slender, with stout counter-unguis seta; urosomite 3 without dorsodistal tooth; telson lobes with 4 small robust setae in row........................................................................... T. pervicax (J.L. Barnard, 1967)

- Gnathopod 1 basis anterior margin with row of simple setae; pereopods 3 and 4 dactylus shortened, oval, with strong counterunguis spine; urosomite 3 with dorsodistal tooth; telson lobes with 8 small robust setae in row......... T. bathyalis sp. nov.