FAM. OLINDIIDAE.—This family appears to be structurally and in development most closely related to the Leptomedusae, and is indeed regarded by Goto[326] as closely related to the Eucopidae in that order. They have two sets of tentacles, velar and exumbrellar; the statocysts are numerous, two on each side of the exumbrellar tentacles. Radial canals four or six. Manubrium well developed and quadrate, with distinct lips. There is an adhesive disc on each exumbrellar tentacle. Genera: _Olindias_, _Olindioides_, _Gonionema_ (Fig. 139), and _Halicalyx_. As in other families of Medusae the distribution of the genera is very wide. _Olindias mülleri_ occurs in the Mediterranean, _Olindioides formosa_ off the coast of Japan, _Gonionema murbachii_ is found in abundance in the eel pond at Wood's Holl, United States of America, and _Halicalyx_ off Florida. Two genera may be referred to in this place, although their {292}systematic position in relation to each other and to other Medusae has not been satisfactorily determined. [Illustration: FIG. 139.—_Gonionema murbachii._ Adult Medusa, shown inverted, and clinging to the bottom. Nat. size. (After Perkins.)] _Limnocodium sowerbyi_ is a small Medusa that was first discovered in the _Victoria regia_ tanks in the Botanic Gardens, Regent's Park, London, in the year 1880. It has lately made its appearance in the _Victoria regia_ tank in the Parc de la Bête d'Or at Lyons.[327] As it was, at the time of its discovery, the only fresh-water jelly-fish known, it excited considerable interest, and this interest was not diminished when the peculiarities of its structure were described by Lankester and others. It has a rather flattened umbrella, with entire margin and numerous marginal tentacles, the manubrium is long, quadrate, and has four distinct lips. There are four radial canals, and the male gonads (all the specimens discovered were of the male sex) are sac-like bodies on the sub-umbrellar aspect of the middle points of the four radial canals. In these characters the genus shows general affinities with the Olindiidae. The difficult question of the origin of the statoliths from the primary germ layers of the embryo and some other points in the minute anatomy of the Medusa have {293}suggested the view that _Limnocodium_ is not properly placed in any of the other orders. Goto,[328] however, in a recent paper, confirms the view of the affinities of _Limnocodium_ with the Olindiidae.