MEDUSAE. 153 



individuals are of a glassy transparency, while older ones are slightly trans- 

 lucent and milky in color, especially in the proboscis, gonads, and marginal 

 tentacles. 



s* 

 s» 

 s» 

 s» 



S" 

 S" 



s» 



S" 



Station 14 ; September 7, 1899 ; N. Lat. 6° 41', W. Long. 137°. 



" 15; " 8, " " 4° 35', " 136° 54'. 



" 16; " 9, " " 2° 38', " 137° 22'. 



" 31; " 19, " S. Lat. 12° 20', " 144° 15'. 



" 32; " 20, " " 13° 37', " 145° 42'. 



" 23, " Lagoon of Rangiroa Island, Paumotus Islands. 



" 24, " off Avatoru pass, Rangiroa. 



October 5, " off Pt. Venus, Tahiti. 



SCYPHOMEDUS-E. 



Charybdea grandis, sp. dov. 



Plate 6, figs. 26-31. 



Adult Medusa. The bell is high and cone-shaped, with a blunt apex. 

 It is 230 mm. high, and 140 mm. in diameter. The gelatinous substance 

 is quite thick and is of a remarkably tough consistency. There are four 

 interradial, wing-like pedalia, the broad sides of which extend outward 

 in a radial direction. These pedalia are each about 40 mm. long, and 

 25 mm. wide. A wide canal extends through the substance of each of 

 them into the flexible portion of the tentacle, which arises from the 

 distal end of the pedalium. The flexible part of the tentacle is about 

 140 mm. long, and its surface is ringed and covered with transverse rows 

 of nematocyst cells (Fig. 28). Four sense organs, or rhopalia (Figs. 

 29, 30), alternate in position with the four tentacles. Each sense organ 

 arises from a deep niche situated about 27 mm. above the level of the 

 velarium. The sense organ is knob-shaped and is mounted upon a short 

 stem, and contains from one to three ectodermal ocelli, and an entodermal 

 otolith. In old medusae there is usually a single, median ocellus in each sense 

 organ, but in a young specimen 30 mm. in height there was a large median, 

 and two small lateral ocelli. These ocelli are all directed so as to perceive 

 objects within the bell-cavity. The velarium is well developed and is sus- 

 pended by four mesenteries, or frenulae, in the regions of the sense organs. 

 Twenty-four short tree-like velar canals (Figs. 26, 31) extend centripetally 



