It is well known that members of the family Cassidae feed exclusively on sand dollars and sea urchins. However feeding is seldom observed in the field, and the prey species of most helmet and bonnet snails (as cassids are commonly called) remain undocumented, and whether certain species are preferred is unknown. It is likely that most cassids are opportunistic predators that will feed on whichever echinoid species is more common or encountered at their respective localities or preferred habitat (see Abbott, 1968; Hughes & Hughes, 1981; Tewfik & Scheuer, 2013). Cassids possess gland ducts that discharge a secretion rich in sulphuric acid to dissolve and penetrate the tests of their victims (Abbott, 1968; Hughes & Hughes, 1981). Perhaps aided by the radula, the test of their echinoid prey may be bored through in a few minutes (Abbott, 1968; Hughes & Hughes, 1981). Empty tests of echinoids (notably Salmacis sphaeroides) bearing bore holes are occasionally encountered in Singapore. However, apart from the prey species herein recorded, grey bonnets attacking or feeding on other echinoids do not appear to have been witnessed thus far.The featured grey bonnet (as well as its sand dollar prey) was collected and deposited in the Lee Kong Chian Natural History Museum at the National University of Singapore under the catalogue number ZRC.MOL.7634.

The specimen is preserved in the Raffles Museum of Biodiversity Research at the National University of Singapore, under the catalogue number ZRC.MOL.5620. Phalium glaucum is considered locally endangered as it was purportedly “[n]ot seen since the early 1970s” (Chou & Tan, 2008: 53). However the remark is erroneous and there are several records and specimens collected from Pulau Ubin, Changi, St. John’s Island, and Cyrene Reef from the mid-1990s to the present day (Tan et al., 2013: 513; unpublished data from Tan Siong Kiat). The present record seems to be the first from Semakau Landfill.

Opinions and declarations Rendered by the International Commission on Zoological Nomenclature

This highly social species lives in pairs or in groups with up to 15 or more members (Shepherd & Shepherd, 2012: 64). Large groups are believed to centre around a female and her offspring from multiple generations (Hunter & Barrett, 2011: 156). The featured sighting may represent the largest group of smooth-coated otters recorded in Singapore

Opinions and declarations Rendered by the International Commission on Zoological Nomenclature