Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus Author Conlan, Kathleen E. 0000-0002-2263-7075 kconlan@nature.ca Author Desiderato, Andrea 0000-0002-2263-7075 kconlan@nature.ca Author Beermann, Jan 0000-0002-2263-7075 kconlan@nature.ca text Zootaxa 2021 2021-03-04 4939 1 1 191 journal article 7102 10.11646/zootaxa.4939.1.1 ee8e66ff-2f2c-47e2-978b-be52996d5b0f 1175-5326 4580622 F33F42D0-A139-4CE3-97D7-1314C12CF86B Jassahartmannae Conlan, 1990 ( Table 13 , Fig. 104 ) Diagnosis. Both sexes: Mandibular palp : article 2, dorsal margin without a fringe of setae. Maxilla 1 : without a cluster of setae at the base of the palp article 1. Gnathopod 1 : basis, anterolateral margin with a row of short setae along its length which may be slender or spine-like; carpus without a single or small cluster of short setae at the anterodistal junction of the propodus. Gnathopod 2 : basis with a row of short setae along the anterolateral margin (setal lengths ±25% of the basis width); carpus and propodus, setae on the anterior margin short and simple (setal length <basis width). Pereopods 5–7 : propodus not expanded anteriorly. Uropod 1 : ventral peduncular spinous process underlying about 50% of the longest ramus. Uropod 3 : inner ramus without spines mid-dorsally (with only the single apical spine). Telson : tip without apical setae (only the usual short setae at each dorsolateral cusp). Thumbed male: Antenna 2 : large individuals without plumose setae on the flagellum and peduncular article 5. Gnathopod 2 : propodus, palmar defining spines produced on a ledge, present in both small and large thumbed males. Adult female: Antenna 2 : without plumose setae on the flagellum and peduncular article 5. Gnathopod 2 : propodus, palm shallowly concave. Remarks. There is an error in the key to species in Conlan (1990) (though the description is correct). The gnathopod 1 carpus lacks a seta or setae at the anterodistal junction with the propodus. There are only 16 specimens known so far from two collections listed in Conlan (1990) , both from New Zealand . Four of these are thumbed males (three major form and one minor form). All males possessed palmar defining spines, suggesting that they may not lose them even if major form. Jassa hartmannae most closely resembles J. justi but they differ in the stonger spination of the propodus of pereopods 5–7, stouter antenna 2 and spinier basis of gnathopod 2 in J. justi than J. hartmannae ( Figs 92 , 104 ). Jassa justi also achieves twice the body length of J. hartmannae .