a crustacean "fixed by its head, and kicking the food into its mouth with its legs." Cirripedes may be roughly divided into two groups, the Acorn Barnacles and the Goose Barnacles. Although dissimilar in general appearance, they pass through identical stages, and are closely related in most of their essential characters. The latter forms are affixed by a chitinous stalk or peduncle, whilst the acorn barnacles are more or less conical and affixed by the base. =Silurian Cirripedes.--= The stalked barnacles are probably the oldest group, being found as far back as the Ordovician period. In Australia the genus _Turrilepas_ occurs in Silurian rocks, _T. mitchelli_ (Fig. 115 A) being found at Bowning in the Yass District of New South Wales. The isolated plume-like plates of _T. yeringiae_ (Fig. 115 B) are not uncommon in the olive mudstone of the Lilydale District in Victoria. [Illustration: =Fig. 115--FOSSIL CIRRIPEDIA.= A--Turrilepas mitchelli, Eth. fil. Silurian. New South Wales B--Turrilepas yeringiae, Chapm. Silurian. Victoria C--(?) Pollicipes aucklandicus, Hector sp. Cainozoic (Oamaru series). New Zealand ] [Illustration: =Fig. 116--LIVING AND FOSSIL CIRRIPEDES.= A--Lepas anatifera, L. Common Goose Barnacle. Living B--Lepas pritchardi, Hall. Cainozoic. Victoria ] =Cainozoic Lepadidae.--= The genus _Lepas_ (the modern goose barnacles) is represented by isolated plates in the Cainozoic (Janjukian) limestones and marls of Waurn Ponds, and Torquay near Geelong: it also occurs in a stratum of about the same age, the nodule bed, at Muddy Creek, near Hamilton, Victoria (_L. pritchardi_, Fig. 116). In New Zealand the gigantic cirripede, _?Pollicipes aucklandicus_ (Fig. 115 C), occurs in the Motutapu beds. =Cainozoic Balanidae.--= The Acorn Barnacles are represented in our Cainozoic shell marls and clays by a species of _Balanus_ from the Janjukian of Torquay; whilst two species of the genus occur in the Kalimnan beds at Beaumaris, Port Phillip, in similar beds in the Hamilton District, and at the Gippsland Lakes. =Phyllocarida: Their Structure.--=