See lilies of the genus Bathycrinus (Echinodermata, Crinoidea: Bathycrinidae) from the North-West Pacific hadal trenches.

In the North-West Pacific hadal trenches, four species belonging to the stalked crinoid genus Bathycrinus were found, three of them are new for science: Bathycrinus kirilli n. sp., B. longipinnus n. sp. and B. rozhnovi n. sp. B. kirilli n. sp. from the Izu-Bonin Trench (9715-9735 m) is the deepest-dwelling crinoid species. Similar characters shared by B. kirilli n. sp. to B. volubilis Mironov, 2000 from the Kuril-Kamchatka Trench (8175-9584 m) related to trench topography with isolated small basins, as previously suggested by Belyaev (1989). Hypotheses explaining why deepest hadal Bathycrinus species display higher abundance than species inhabiting shallower environments are discussed.

A new species of Western Atlantic sea lily in the family Bathycrinidae (Echinodermata: Crinoidea), with a discussion of relationships between crinoids with xenomorphic stalks.

A new species in the family Bathycrinidae is described from abyssal depths from the Bahamas. It is referred to the recently established genus Discolocrinus, which formerly comprised a single species D. thieli Mironov, 2008 from the Eastern Pacific. Discolocrinus iselini n. sp. is characterized by large body size, high tegmen with tube-like upper region, extremely elongated IBr1 and IBr2, large knobby processes on primibrachials, and overgrowth of soft tissue on the pinnules, the tissue containing numerous perforated or imperforate ossicles of varying size and form. Differences between Discolocrinus and other bathycrinids may seem to be of taxonomic importance at the family level, but knowledge of the morphology and variability of both species of Discolocrinus is incomplete and, until a richer material becomes available, the genus should remain in family Bathycrinidae. Representatives of five families with xenomorphic stalks were examined to characterize the genera on the basis of number or form of knobby processes. These processes occur in two families with differing external morphology: ten-armed Bathycrinidae and five-armed Bourgueticrinidae. They also occur in the comatulid family Atelecrinidae. This similarity might seem to indicate a close relationship between the three families. However, morphological analysis supports the separation of the families Caledonicrinidae and Septocrinidae from Bathycrinidae despite the fact that they share a xenomorphic stalk and IBr2ax. These conclusions are in agreement with results of recent molecular studies.