« Shell internal, posterior, consisting of a flat, solute spiral whorl and a minute spire, the inner rim of whorl calcified, outer part membranous. » – H. A. Pilsbry: Manual of conchology, structural and systematic ser.1 vol.16, Philadelphia 1895; p.43.
 

« In the Prospetto della Classe dei Vermi (1804) Renier counts as XIth the genus AGLAJA in the first order - Mollusks - (page xvi), adding the following note: “I have named this new genus of mollusks AGLAJA, name of one of the three Graces, meaning Cheerfulness (άγλαία, Laetitia, enjoyment) and even splendor (άγλαός, splendidus, which also means: worthy of great admiration). Thus giving a fabulous name also to this sort of living, as was done by Clione, Doride, Tritone, Talia etc. I combine, with the meaning of the word Aglaja, also to express some properties of the species hitherto observed by me of this new genus; for they have a shine in some places of the body. And they are so slightly coloured, that they bring admiration to those who observe them live in sea water.” » – G. Meneghini: Osservazioni postume de zoologia adriatica, Venezia 1847, p.3. The anatomical description is given in the plate VIII, published in 1807. We learn here that the animal is devoid of shell. In fact, the shell is very thin, fragile, small, more chitinous than calcareous, so much so that it may have escaped Renier’s poetic observation.
 

« Shell quite internal, triangular, spire minute, inner lip with a small spoon-shaped projection. […] Aglaia (of Renier) appears to be its nearest ally; but l am unable to place it in that genus, as it differs from the species figured in Adams’ Genera in being much more elongated, in the cephalic disc being larger and projecting beyond the foot, in the branchiae being smaller and always concealed by the mantle, and in the side-lobes of the foot being closely appressed to the sides of the animal, and not spreading.  » – T. F. Cheeseman: “On a new genus of Opisthobranchiate Mollusca”, Transactions and Proceedings of the Royal Society of New Zealand vol. 13, Wellington 1880, p.224.
 

The shell is external, partly covered by the mantle, and looks like that of a PHILINIDAE.