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This species wasn't well described by A.Adams (1855) from the 'eastern seas'. Let me quote the redescription of it by Price et al. (2011), page 31:
"External morphology: The living animal is uniformly white (Figure 2E) and approximately 2.5-4cm in length. The cephalic shield is longer than the posterior shield, and the parapodial lobes are thick and muscular (Figures 25A, 26 A). A notch may be present or absent on the posterior shield but seems to be absent in poorly preserved specimens."
Very similar is Philine paucipapillata Price, Gosliner & Valdés, 2011 also from the Indo-Pacific region, which differs only internal by the penial papilla and by "the undulating denticular margin on the masticatory border of the inner lateral teeth" Price et al. (2011) .
A junior synonym of this species is Philine argentata Gould, 1859.
Philine orientalis has been reported from Japan, Malaysia, the Philippines, and had recently been introduced to California, USA.
Adams A. (1855 ["1854"]). Descriptions of some new species of Lophocercidae and Philinidae, from the Cumingian collection.
Proceedings of the Zoological Society of London. 22: 94-95.,
available online at https://www.biodiversitylibrary.org/item/96679#page/384/mode/1up page 94
Price R. M.; Gosliner T. M.; Valdés A. (2011). Systematics and phylogeny of Philine (Gastropoda: Opisthobranchia), with emphasis on the Philine aperta species complex.
The Veliger. 51(2): 1-58. [26 May 2011]., available online at http://biodiversitylibrary.org/page/42497280
How to cite:
Köhler, E. (2021), published 30 March 2021, Philine orientalis A. Adams, 1855
available from https://www.Philippine-Sea-Slugs.com/Cephalaspidea/Philine_orientalis.htm