F. S. CONANT ON THE CUBOMEDUS^E. 9 



of about 45 with the longitudinal axis of the bell. In the preserved 

 specimens they are bent in toward the axis by the contraction of the 

 strong muscles at their base, in which position they are figured by Glaus 

 for C. marsupialis (78, Taf. I., Figs. 1 and 2). 



The pedalia are in reality processes belonging to the subumbrella, as 

 will be shown in the section treating of the vascular lamella. They are 

 composed chiefly of gelatine covered with thin surface epithelium and 

 carrying within the gelatine the basal portion of the tentacle canals. 

 They have received various names at the hands of the writers. Gegen- 

 baur called them " Randblatter." Glaus gave them the name of "Schirm- 

 lappen," and incorrectly homologized them with the marginal lobes of 

 other Acraspeda. Claus's error was corrected by Haeckel, who termed 

 them "Pedalia" or "Gallertsockel," and homologized them with the 

 pedalia of the PeromedusaB. Besides furnishing a base of support for the 

 tentacles they may perhaps also serve as steering apparatus, a function 

 for which their thin blade-like form would be admirably adapted. 



Internal to the base of each pedalium, between it and the velarium, 

 is found a funnel-shaped depression of the ectodermal surface. This is 

 shown in Fig. 5 (ft) in longitudinal section, and in cross-section in Fig. 16. 

 In the latter figure the epithelium of the outer wall of the funnel (mt) is 

 shown much thickened, the result of a stout development of muscle 

 fibres. These are the muscles that in the preserved specimens cause the 

 inward contraction of the pedalia referred to above. 



4. Sensory Clubs (marginal bodies, rhopalia). In spite of their posi- 

 tion above the bell margin, the four sensory clubs, representing as they 

 do transformations of the four perradial tentacles, are properly classed 

 with the pedalia and interradial tentacles as appendages of the margin. 

 They lie protected in somewhat heart-shaped excavations or niches in 

 the perradial areas of the exumbrella. Each sensory niche is partially 

 roofed over by a covering scale, a hood-like projection from the exum- 

 brella. Below the covering scale the water has free access to the niche 

 and to the sensory club within it. The sensory club consists of a 

 hollow stock directly homologous with tentacle and canal, and a termi- 

 nal, knob-like swelling, the sensory portion proper. The latter con- 

 tains on its inner surface the surface turned towards the bell cavity 

 two complicated unpaired eyes with lens, retina, and pigment, lying one 

 above the other in the median line ; and at the sides of these, two pairs 

 of small, simple, pigmented, bilaterally symmetrical eye spots. At the 

 end of the club, that is, on its lowermost point, lies a sac that contains a 

 2 



