108 NEW INVERTEBRATA FROM 



the bell. Radial tubes four, narrow, simple, unbranched. 

 A well-marked velum closes in part the entrance to the 

 bell cavity. 



The proboscis is simple, without labial appendages. It 

 is richly pigmented near the oral end and at its attachment 

 to the inner bell walls. A spherical pigment spot indicates 

 the terminus of three of the radial tubes on the marginal 

 vessel. These tubes are destitute of tentacles. 



A single, long, flexible tentacle arises from the point of 

 union of one of the radial tubes with the marginal tube. 

 This tentacle is ribbed throughout its entire length with 

 ferrules, composed of nematocysts, as shown in the figure. 



Immature forms of the young appear budding from 

 the base of the single large tentacle near its attachment. 

 These young medusse vary in size from a simple enlarge- 

 ment to an individual just ready to separate from its at- 

 tachment and approximately resembling the adult. Many 

 of these have the single long tentacle developed, but in 

 none were the other tentacles comparatively as long in the 

 young as in the adult. In the very young bud, all the ten- 

 tacles are simple protuberances of equal size. I have espec- 

 ially considered the relative sizes of all the tentacles in the 

 young, for it seemed to me that possibly the genus might 

 betray in those stages affinities with medusas with four ten- 

 tacles. It would seem, however, that the predominance in 

 size of a single tentacle dates back to very early conditions. 



There is no apical extension of the umbrella or bell, and 

 no remnant of a " funiculus," or tube by which the radial 

 system of chymiferous tubes were once connected with a 

 hydroid. 



The structure of the tentacle closely resembles that of 

 Steenstrupia. The movements of the medusa are so ac- 

 curately described by Forbes for his species, and apply so 

 well to the California!!, that I have taken the liberty of 



