A large and important group of the higher Crustacea, but confined to the older rocks of Victoria, is the order _PHYLLOCARIDA_. This seems to form a link between the Entomostraca, including the bivalved Ostracoda and the well-known group of the lobsters, shrimps and crabs. The body of these phyllocarids consists of five segments to the head, eight to the thorax, and from two to eight to the abdomen. The portion usually preserved in this group is the carapace, which covers the head and thorax, and although often in one piece, is sometimes hinged, or otherwise articulated along the back. In front of the carapace there is a moveable plate, the rostrum or beak (Fig. 117). There are two pairs of antennae to the head, and the animal is provided with a pair of stalked compound eyes. The thoracic segments are furnished with soft leaf-like legs as in the Phyllopods. The abdomen is formed of ring-like segments, and generally terminates in a sharp tail-piece or telson, often furnished with lateral spines. In many respects the ancient phyllocarids correspond with the living genus _Nebalia_, which is found inhabiting the shallow waters of the Mediterranean and elsewhere. [Illustration: =Fig. 117--Ceratiocaris papilio, Salter.= Silurian. Lanarkshire. (_After H. Woodward_) ] [Illustration: =Fig. 118--ORDOVICIAN PHYLLOCARIDS.= A--Rhinopterocaris maccoyi, Eth. fil. sp. L. Ordovician. Victoria B--Caryocaris angusta, Chapm. L. Ordovician. Victoria C--Saccocaris tetragona, Chapm. L. Ordovician. Victoria ] [Illustration: =Fig. 119--SILURIAN PHYLLOCARIDS.= A--Ceratiocaris pritchardi, Chapm. Silurian. Victoria B--Ceratiocaris cf. murchisoni, Agassiz sp. Silurian. Victoria C--Ceratiocaris pinguis, Chapm. Silurian. Victoria ] =Ordovician Phyllocarids.--= Phyllocarids of the Lower Ordovician slates are referred to the genera _Rhinopterocaris_, _Caryocaris_, _Saccocaris_ and _Hymenocaris_. The first-named is the commonest type; and is found in slates of the Lancefield, Bendigo and Castlemaine Series at the localities named, as well as at Dromana. _Rhinopterocaris_ (Fig. 118 A) is readily distinguished by its long--ovate outline, and this, together with its wrinkled chitinous appearance makes it resemble the wing of a dipterous insect. _Caryocaris_ (Fig. 118 B) is a smaller and narrower form which occurs in the Victorian Lower Ordovician slates, as well as in ice-borne blocks derived from the Ordovician, at Wynyard, in N.W. Tasmania. =Silurian Phyllocarids.--=