PHIALUCIUM. 157 



importance as is the form of the tentacular bulbs. They usually occupy 

 the distal two thirds of the canals, but occasionally extend the entire length 

 of a canal. Such a variation is to be seen on the different gonads of the 

 specimen photographed (PI. 6, fig. 8). Gonads are present, though of small 

 size, even in specimens only 1.5 mm. in diameter. In females the ova are 

 very large. The collection contains both males and females. 



The manubrium is short, and quadrate in outline ; the mouth surrounded 

 by four simple lips. 



Color. — The Medusae were entirely colorless in life. 



The difference in number of tentacles and of otocysts between the present 

 specimens and Mayer's (: 00'') account of P. discoida might perhaps have 

 seemed of specific importance had I not had access to a West Indian series, 

 from near the type locality. I am now convinced that these differences are 

 due to different stages in growth, a conclusion in no way negatived by the 

 large size (4 mm.) of Mayer's specimens, since his description was written 

 from fresh specimens, while the measurements in the present account were 

 taken from preserved material ; but whether or not my identification of 

 this series with the form described by Mayer is correct, the significant 

 fact of the identity of the Pacific with a West Indian form remains. 



Phialucium Maas, 1905. 



sens. em. 



Eucopidae with numerous tentacles and otocysts (number indetermi- 

 nate) ; with rudimentary as well as large tentacles; with or without cirri. 

 Rudimentary tentacles may be developed at a late stage in growth. 



Phialucium was proposed by Maas (: 05) as a subgenus ; but it is worthy 

 of full generic rank. 



As defined by Maas it lacks cirri ; but a species in the present collection 

 which has cirri flanking the tentacles, in other respects so closely resembles 

 the type species, P. virens Bigelow (: 04), that it is best to discard the 

 presence or absence of these organs as a generic character. The genus 

 may be regarded as intermediate between Phialidium and Eirene, since 

 West Indian specimens, to be described below, acquire a rudimentary 

 peduncle when fully grown, but only long after the appearance of the 

 gonads. Up to the present time two species only have been described 

 which are referable to this genus, Oceania virens Bigelow (: 04) 



