NEW TYPE OF MALACOSTKACOUS CEUSTACEAN. 



13 



Maxillipeds 



Peraeopoda 



Pleopoda 



Uropoda and telson 



Oviduct 



Spermatheca 



Vas deferens 



Copnlatory organs 



Anaspides. 



Pediform, 8-jointed ; with two branchiae 

 and exopodite, and two gnatho- 

 basic lobes. 



Anterior ones 8-, posterior oDes 7- 

 jointed. Each, except last, with 

 2 branchiae. A swimming-exopod 

 on the first five pairs and a 

 rudimentary one on the sixth 

 pair. 



Natatory, eudopodite rudimentary, 

 first two pairs modified in male. 



Together forming a fan. 

 ? 

 ? 

 ? 



The endopodites of the 1st and 2nd 

 pleopods. 



Koonunga. 

 Relatively stouter, 7-jointed, branchiae 



and exopod similar, no gnatho- 



basic lobes. 

 Of similar form, all 7-jointed. Each 



except last pair with 2 branchiae. 



Swimming-exopod on the first 



five pairs only. 



Quite similar, but endopodite absent, 

 except in first two pairs of male. 

 Similar. 



Opening on the antepenultimate legs. 

 On sternum in front of last legs. 

 Opening on the last legs. 

 Similar. 



It is obvious from a review of these two forms that Koonunga, more particularly, shows 

 conspicuous modifications in the direction of the sessile-eyed characters, notably in the 

 coalescence of the first thoracic segment and. head, the character of the eyes, the mouth- 

 parts, and also in the absence of any antennal scale. 



I was hopeful that Koonunga would have shed considerable light on the Cumacea and 

 Tanaidacea, but after careful examination I fail to find any of importance. The divergent 

 sessile-eyed branch of the stalk-eyed stem seems to have a wide gap between Koonunga 

 and other forms. It may be mentioned, however, that in Koonunga there is a good deal 

 that points to the Amphipod type, at least, more than to the Isopod, notably in the general 

 form of the body and its somites, the position of the eyes, which are above the base of the 

 antennas, not lateral to them, as in the Isopoda, the shape of the first maxillse, the pleopoda, 

 and also in the short terminal somite and its uropoda, together with the telson ; but there 

 are \evj many characters of dissimilarity to that order, as well as to the other sessile-eyed 

 forms ; of these the following characters may be mentioned : the absence of a brood- 

 pouch, the antennal peduncle having four instead of five joints, the absence of a secondary 

 cutting-plate (lacinia mobilis) in the mandibles, and the possession of an auditory organ 

 at the base of the upper antennas. 



Undoubtedly there is a much closer relationship with the stalk-eyed forms, and of these 

 it is nearest to the Mysidacea and Euphausiacea, but, although there are many characters of 

 agreement, there are such marked and apparently dominant characters of difference that 

 I believe it better placed in a separate order from either of them. Of the two, Koonunga 

 is nearest to the Euphausiacea, at least in its external anatomy, notably in the uniformity 

 of the maxillipeds and thoracic limbs, the mandibles not having a spine-row, the pleopoda, 

 with their sexual differentiation, and the absence of a brood-pouch. One would have 

 expected that it would have been in closer relationship to the Mysidacea, but, judging 

 from its outward appearance alone, this is not so. 



