Journal 
INTRODUCTION
The genus Henricia Gray, 1840 is a species-rich genus comprising 95 species worldwide (Wakita et al. 2019;Ubagan et al. 2020). Due to the lack of a stable phylogenetic definition, many species have been described and assigned to Henricia based only on traditional diagnosis (Fisher 1911;Hayashi 1940;Djakonov 1950;Madsen 1987;Clark and Downey 1992;Clark and Jewett 2010). The number of Henricia species has increased, especially in the northwestern part of the Pacific; however, high diversity within the genus has persisted. Recently, three new species, H. epiphysialis from the East Sea of Korea (Ubagan et al. 2020), and H. margarethae and H. fragilis from the deep-sea of Sagami Bay and Ogasawara of Japan (Kobayashi et al. 2021), have been added to the genus Henricia. Species from the surrounding regions of the northwestern Pacific, Japan have contributed to defining useful diagnostic characters of the genus Henricia. In particular, two distinguishing characteristics (i.e., the width of adambulacral plates, the ratio of two measurements in ambulacral plates to the length of interradius) are useful for differentiating other related species of genus Henricia (Wakita et al. 2019). However, these morphological characteristics could be plastic to some degree, and the ossicle shape and spine number may vary with the size of the animal (Madsen 1987). One approach to reducing the complications of species diagnosis is to focus on regional fauna in taxonomic revisions (Eernisse et al. 2010).
MATERIALS AND METHODS
The Henricia specimen was collected from waters near Jukbyeon, Korea (37°02ʹ20.2ʺN, 129°25ʹ49.58ʺE), using fishing nets on May 24, 2013. This specimen was preserved in 95% ethanol, and the following morphological characteristics were examined: the size of the disk, upper and proximal portions of the arms, number of abactinal spines, shape of the abactinal and actinal skeleton, and number of adambulacral spines. The morphological features of the specimen were photographed using a scanning electron microscope ( JSM-6510; JEOL Ltd., Tokyo, Japan), a stereomicroscope (Nikon SMZ1000; Nikon Co., Tokyo, Japan), and a digital camera (Nikon D7000). The abbreviations for the measurements were those used by Ubagan and Shin (2020).
SYSTEMATIC ACCOUNT
Class Asteroidea de Blainville, 1830
Order Spinulosida Perrier, 1884
Family Echinasteridae Verrill, 1870
Genus Henricia Gray, 1840
Henricia hayashii (Djakonov 1961)
Henricia hayashii (Djakonov 1961), pp. 22, 23, pl. 2, fig. 8, pl. 13, figs. 54, 55; Chichvarkhin & Chichvarkhina, 2017a: p. 208, fig. 4A; 2017b: p. 26, fig. H. Chichvarkhin et al. 2019: p. 20, fig. 8A-N; Mah, 2021: 369111.
Material examined. One specimen: Jukbyeon (37°02ʹ 20.2ʺN, 129°25ʹ49.58ʺE), 24 May 2013, MERBK-A-1259, fishing net, Shin, S. and Lee, T.
Description. Arms five, long, slender, gradually tapering to tips (Fig. 1A, B). Abactinal paxillae clustered, containing six to thirty-five slender spinelets, forming slightly curved series around the papular area, and not covered with skin (Fig. 1C). Denuded abactinal spines, slender, bearing seven to 11 pointed apical thorns (Fig. 1J). Papular areas irregular shape, wider than abactinal plate areas, containing two to six papulae in each area (Fig. 1H). Abactinal skeleton openmeshed, reticulated, comprising semi-triangular, rod-like form, small ossicles present inside papular areas (Fig. 1G). Madreporite situated near center of disk, circular in form, slightly elevated, and bearing spines larger than abactinal spines (Fig. 1F). Actinal plates close-meshed, with narrow spaces of papular areas with one or two papulae larger than abactinal plates. Superomarginal, intermarginal, inferomarginal, and ventrolateral plates distinguishable. Superomarginal plates bearing nine to 12 spines, reaching tip of arm. Inferomarginal plates reniform in shape, compact, and larger than surrounding plates, bearing more than 30 spinelets. Ventrolateral plates rounded cross shape, compact, bearing 13 to 16 spines, reaching one-half length of arm (Fig. 1I). Adambulacral armature comprising 14 to 18 bluntly tip spinelets; inner spines being longer, larger than outer spines, and arranged in two or three transverse or zigzag rows (Fig. 1D, K). Oral plate bearing two bluntly tip spines (Fig. 1E). Furrow spine single, situated deeply on furrow edge, densely covered with adambulacral spines (Fig. 1D).
Size. R=82 mm, r=11 mm, R/r=7.4.
Habitat. Hard substrates (rocks).
Color. Body color was light brown in alcohol.
Distribution. Korea (East Sea), Russia (Vostok Bay).
Deposition. The collected specimen was deposited in the Marine Echinoderm Resource Bank of Korea, Sahmyook University, Seoul, Korea.
Remarks.Henricia hayashii was first introduced by Russian zoologist, A. M. Djakonov in 1961. H. hayashii is similar to H. reniossa by its body size but differs in the shape and arrangement of the abactinal skeleton. Compared to other species with slender, tapering arms such as H. leviuscula, the primary differences are the following: 1) abactinal spines (H. hayashii: slender; H. leviuscula: granular and solid glassy tip); 2) abactinal skeleton (H. hayashii: open meshed, reticulated; H. leviuscula: closed meshed, imbricated). Thus, H. hayashii allowed for the establishment of different morphological characteristics compared to other species of Henricia with slender arms. Our specimen H. hayashii have slight differences compared to the holotype description from Djakonov (1961) in terms of the furrow spines: our specimen possess single furrow spine, while Djakonov’s description includes double deep furrow spines. In addition, the size of our specimen is smaller (R=82 mm) compared to the original specimen (R=142 mm). However, this morphological difference does not make the specimens distinct from each other. Therefore, we consider that our specimen to be the same species as that described by Djakonov (1961). H. hayashii is newly reported in Korean fauna.
