Shell average to small for the genus: most adult shells measure between 7 and 12 mm in length, although the species grows to 20 mm. Shells larger than 14 mm are rare. The shells are thick shelled, relatively high in shape when viewed from the side. The perforation on top is elongate, with two narrowing areas. In the center the widest. Outside surface covered by with about 35 dominant primary radiating ribs. There are only a few secondary ribs to be observed, mainly on the backside - the short side behind the perforation. On the big slope there are about 16 con-centric ribs crossing the radiating ribs. They number only about 12 on the small slope. Where these concentric ribs cross the radiating ribs, strong knobs are formed. In between, deep pits are formed. Inside white, but the outside coloration shines through. Around the perforation a thickening, with the typical Diodora shape. On the periphery, where the radiating ribs end, a small slit is formed. So, the periphery can be called deeply incised. The coloration is quite complicate: fresh shells are dark green colored with a white fleck pattern that becomes more extensive as one moves to the perforation. There are about 8 reddish - bordeaux - colored radiating ribs. We refer to the plates to perfectly understand shape and coloration and the details.

We here compare the species with other Indo-Pacific Diodora with which it was confused in the past, or that bear some similarities.

Diodora quadriradiata (Reeve, 1850)
Two syntypes of the BMNH have been figured by Higo et al. (2001). We are not certain that both syntypes belong to the same species. The shells are black and white in coloration, lacking the greens and reds. The shape is different: D. quadriradiata is more broad on the side of the large slope downwards compared to shells of D. magnified n. sp. They also have a bigger number of ribs with alternating primary and secondary ribs, while secondary ribs are most often absent in D. magnified n. sp. The syntypes of D. quadriradiata are also much larger than most D. magnifica n. sp. They measure respectively 18 and 19 mm in length.

Diodora cruciata (Gould, 1846)
Described from the Sulu Sea, has a shell very similar to the new species. However, it can be distinguished immediately by its pure white and black condition with a "cross pattern". The shells of D. cruciata are in general, flatter, not so high shaped as D. magnifica n. sp. when seen from the side and the size is slightly smaller. We refer to the plates for easy differentiation of both species.

Diodora ruppellii (G. B. Sowerby I, 1835)
Is an Indian Ocean species that occasionally may have a similar pattern. It is however, much bigger in size, has more ribs and is much broader shaped. The perforation is different: more rounded and not with a 3-hole linked shape as in D. magnifica n. sp.

TYPE LOCALITY
Philippines. Cebu. Maya. 3 m deep.

DISTRIBUTION
At present only known from the central Philippines: Aliguay Island; Balicasag Island; Bohol; Cabilao Island; Calangaman Island; Camotes Islands; Caubian Island; Cebu: Liloan, Sogod, Maya & Moalboal; Leyte; Mactan Island; Olango Island; Palawan; Pandanon Island; Quatro Islands; Sumilon Island.