Perotrochus wareni: The « Waren's Slit Shell » is a small pleurotomariid endemic to New Caledonia, characterised by a fine pustulose sculpture. For many years, it was considered to merely represent a 'pustulose form' of P. caledonicus Bouchet & Metivier, 1982 which occured allopatrically and shared with it similar size, colour, and shape. The type specimen of P. caledonicus, however, had smooth and unbeaded spiral cords; no clear intergrades between the two forms were known. Only very recently, a study using both morphological and molecular data finally revealed that the two in fact represent two distinct lineages and are separate species. The 'pustulose form' was therefore described anew, as Perotrochus wareni, shown here. Though the two species appear to occur allopatrically in New Caledonia, P. wareni is more comm.on in the northern New Caledonia while P. caledonicus is predominantly found in the southern areas around Isle of Pines. They also differ slightly in depth preference, with P. wareni occuring mostly around 350m deep and P. caledonicus slightly deeper at around 400m. Furthermore, the range of P. wareni extends westwards to Lansdowne Plateau in the Coral Sea but the range of P. caledonicus does not appear to reach the Coral Sea at all. The population from Chesterfield Plateau in the Coral Sea, previously attributed to P. caledonicus, was revealed to be a further distinct species in the same study and was named P. pseudogranulosus Anseeuw, Puillandre, Utge & Bouchet, 2015. It inhabits hard substrates and is a carnivorous grazing gastropod feeding on demosponges. Typical shell length around 40mm. but extremely large specimens may exceed 70mm. Though it is locally somewhat comm.on, high quality specimens are uncomm.on on the shell trade market.

Perotrochus wareni: Finding Place: Grand Passage, North of New Caledonia.