726 EDWAKU T. BROWNE. 



A. Agassiz figures the same type of radial canal system for specimens taken on the 

 American side of the Pacific Ocean. He records the presence of clusters of nematocysts on 

 the ex-umbrella. Haeckel, however, considered that Agassiz's specimens were specifically distinct 

 from those described by Brandt and gave to them a new specific name— P. brevicirmta. Murbach 

 and Shearer have given a description, without figures, which practically confirms Agassiz's 

 observations. 



The specimens which have been described by the above authors had all reached the 

 adult stage, but not quite the same stage in growth. Murbach records 54 tentacles for the 

 laro-est specimen, Agassiz gives 64 tentacles, and Mertens' figures show about 70 tentacles. 

 The early and intermediate stages of this species have not yet been recorded. 



Distribution. North Pacific: Kamchatka (Mertens, vide Brandt). British Columbia: 

 Gulf of Georgia (A. Agassiz). British Columbia : Victoria Harbour (Shearer). 



Prohofcidactyla occidentalis (Fewkes), 1889. 



Willia occidentalis, Fewkes (1889, p. 109, PI. V. fig. 3). 



The four main radial canals run straight to the margin of the umbrella, and each canal 

 gives off two opposite lateral branches, which again branch. Each main canal has therefore 

 five terminations leading direct into five tentacles. A single cluster of nematocysts lies on the 

 ex-umbrella between every two tentacles. Fewkes states that the " ovaries are four in number, 

 arranged at the base of a four-parted stomach." The medusa has twenty tentacles, with bright 

 reddish basal bulbs. 



Distribution. North Pacific: California; Santa Cruz Is. (Fewkes). 



Proboscidactyla ornata (McCrady), 1858. 



Willsia ornata, McCrady (1858, p. 149, PI. IX.); L. Agassiz (1862); A. Agassiz (1865, p. 171, 

 figs. 274 a— 279). Dyscannota dysdipleura, Haeckel (1879). WiUetta ornata, Haeckel (1879). 

 Willia ornata, Fewkes (1882, p. 299, figs. 22—23). 



In the earliest free-swimming stage the medusa has four main radial canals, without any 

 branches, and four tentacles (Fewkes, 1882). Agassiz (1865) has figured the intermediate stages 

 showing that each main radial canal gives off a branch which runs to the margin of the umbrella. 

 Later on a second branch appears on the side opposite to the first branch, and this also goes 

 to the margin. McCrady (1858) described the adult stage with four main radial canals, each 

 with three terminal branches and sixteen tentacles. Owing to the growth of the umbrella 

 during the development of the canal system the main canals become curved and in the adult 

 the appearance of the system is correctly expressed by saying that each main canal is twice 

 dichotomously branched. The development of the canal system in this species is similar to 

 that of Willia stellata, and can be conveniently separated into four stages. 



First stage. Four radial canals without branches. 4 tentacles. 



Second stage. Each main canal with one branch. 8 tentacles. 



Third stage. Each main canal with two opposite branches. 12 tentacles. 



Fourth stage. Each main canal with three branches. 16 tentacles. 



