SCYPHOMEDUSAE COLLECTED BY STEAMER ALBATROSS. 



225 



which are largest and most abundant at the center of the exumbrella 

 but disappear near the margin and are not seen over the lappets. 

 Near the center of the exumbrella these papillae are about 6 to 10 

 mm. apart and each is about 35 to 40 mm. long and 3 to 5 mm. wide 

 at the base ; they are conical, usually more or less curved, and taper 

 to pointed ends. 

 Their surfaces are 

 thickly covered with 

 nematocysts, which 

 give a bristling ap- 

 pearance to the disk 

 of the medusa. 

 Eight rhopalia 

 which lack ocelli in 

 specimens preserved 

 in formalin or alco- 

 hol. On the exum- 

 brella side above 

 each sense club there 

 is a shallow, heart- 

 shaped, sensory pit 

 with dendritic 

 ridges over its floor. 

 The rhopalia are 

 flanked by very 

 small, oval, ocular 

 lappets only 3 mm. 

 long and 2.5 mm. 

 wide. There are 32 

 (4X8) velar lap- 

 pets, which are most 

 extraordinary, each 

 being 90 to 100 mm. 

 long and tapering 

 gradually from base 

 to tip. They are 

 modified so as to re- 

 semble superficially 

 tentacles of semaeostomous Scyphomedusse. They trail downward 

 from bell margin, waving flexibly to and fro, as do veritable 

 tentacles. I can find no muscles in these lappets, however, and 

 Light confirms the statement that they can neither contract nor 

 elongate. They are deep clefts in the exumbrella surface between 

 the lappets, but these clefts are bridged over by a thin subum- 



101825°— Bull. 100—17 15 



Fig. 22. — Lobonema smithii. A, Diagram showing the plan 



OP STRUCTURE OP THE MOUTH-ARMS. B, SIDE VIEW OF ONE 

 OF THE MOUTH-ARMS. C, RHOPALIUM AND ONE OF TBE 

 LONG, TAPERING MARGINAL LOBES. 



