Raspberry Jelly (Aeginura grimaldii)
Tiny members of a very small jellyfish order called narcomedusae, the 4-5 cm raspberry jelly (Aeginura grimaldii) can be found between 530 and 3400 meters below the surface in the open ocean. Narcomedusae generally have a small number of tentacles (eight, in this case) and a thin, lobed, dome-shaped bell. The tentacles are attached to the bell at a point higher than many other jellies, and usually have a small pouch above each attachment point.
The red color of their bell (with slightly paler tentacles) makes them effectively invisible in the darkness of the deep sea, due to rapid absorption of the long-wavelength red spectrum of light. They are ambush predators, known to hold their tentacles out horizontally when hunting to catch unwary prey.
We have encountered Aeginura jellies near Axial Seamount, often directly above hydrothermal vent fields like International District.
References:
Wikipedia
WoRMS Taxonomic Database
MBARI personal communication (Matsumoto, G.)
