HYDROMEDUSAE 3„ 



Since W. mutabilis was first described from the Falkland Islands (Browne, 1902) it 

 has been recorded once from the same locality (Browne, 1908) and recently (Thiel, 

 1938) from two localities in South America: Patagonia Bank and north-east of Puerto 

 Madryn. Vanhoffen (1912 b) also records it, though with some doubt, from Punta 

 Arenas in the Strait of Magellan, where several young specimens were found. According 

 to Vanhoffen a small tentacle was present between every two of the larger tentacles 

 which are opposite the terminal ends of the branched radial canals, whereas he failed to 

 see any canals leading to the small tentacles. As stated above, the canals leading to very 

 young tentacular bulbs may be very difficult to see, and it seems probable that they have 

 actually been present in Vanhoffen's specimens, though he has not observed them. 

 Those from Punta Arenas were all six-rayed ; nevertheless, considering the area where 

 they were found, it seems probable that they really belonged to W. mutabilis. 



Family MOERISIIDAE 

 Genus Tiaricodon Browne (1902) 



Generic characters. Moerisiidae with four perradial tentacles. Stomach with four 

 perradial lobes extending along a broad peduncle; mouth with four distinct lips. 

 Gonads upon the stomach and its lobes. 



This genus was erected for the species Tiaricodon coendeus from the Falkland Islands 

 and was originally referred to the Tiaridae, subfamily Protiarinae. Mayer (1910, p. 73) 

 was inclined to refer T. coendeus to the genus Corynitis (the name changed into LinviUea, 

 p. 719, because Corynitis was preoccupied) among the Codonidae. In LinviUea, how- 

 ever, the gonads are entirely restricted to the lateral walls of the stomach, forming four 

 deep, interradial grooves, but not extending along the radial canals, and the structure of 

 the tentacles is quite different from that of Tiaricodon. Vanhoffen (191 2 h, p. 6), who 

 had examined some specimens of T. coendeus from South America and cut sections of 

 the manubrium, likewise referred the species to the Codonidae and placed it in the 

 same genus as Corynitis {LinviUea) agassizii McCrady, but retained the generic name 

 Tiaricodon. As a matter of fact, Tiaricodon is essentially like a large Moerisia or 

 Caspionema and is only distinguished from these genera by the possession of a short 

 stomachal peduncle and four distinct oral lips armed with nematocysts. In the present 

 paper it is, therefore, referred to the Moerisiidae. 



Tiaricodon coeruleus Browne (Plate XVIII, figs. 1-6; Plate XIX, figs. 8-1 1). 



Tiaricodon coeruleus Browne, 1902, p. 276. 



Corynitis (?) coerulea Mayer, 19 10, p. 73. 



Tiaricodon caendeus Vanhoffen, 19126, p. 6, Taf. I, fig. 2; Taf. II, figs. 2-6. 



Specific characters. Adult: Umbrella bell-shaped, with a rounded summit, about 

 as high as broad; gelatinous substance thick, especially at the apex. Exumbrella smooth 

 and not covered with nematocysts. Velum narrow. Stomach a quadrangular tube 

 extending down nearly to the velum, and situated on a short, broad peduncle, forming 

 four large perradial, sac-like lobes. Mouth with four perradial lips, about as wide as 



