Notoscopelus caudispinosus anal fin and 11 to 13 in the pectoral fins. There are groups of photophores (small light organs) on the head and sides of the body. Above the caudal peduncle there is a row of eight to nine luminous scale-like segments in adult males, but male fish lack luminous organs above the eye and on the cheek. "N. caudispinosus" differs from closely related species in having fewer than 15 gill rakers. This species has a wide oceanic distribution in deep water habitats. It is found in the eastern Atlantic Ocean between the equator and about 35°N, but is absent from
Operculum (gastropod) valves of a bivalve species, then for many years after that they were considered to be a form of paired or single operculum-like structures belonging to ammonites. More recently the aptychus or paired aptychi have been hypothesized to be a jaw apparatus of ammonites. Perhaps the most essential function of the operculum in gastropods is to allow snails to resist drying out, or desiccation. This is very important in intertidal marine snails during low tide, and this also enables operculate freshwater and land snails to survive periods of drought and dry weather. In those marine species where the operculum completely