A. Tapering, cylindrical cone-shaped fossils 1. Cone-shaped with longitudinal partitions or septa Coral 2. Fossils with septa or sutures; tapering at one end Cephalopod 3. Shell without internal partitions or sutures a. Shell large heavy, external longitudinal ribs. Cretaceous only Rudistid b. Shell small, tusk-shaped open at both ends. Rare in Paleozoic and Mesozoic Scaphopod B. Disc or dome-shaped fossils 1. Star pattern on top Echinoid 2. Subconical small pits or pores on top Bryozoan 3. Small disc-shaped (less than ½ inch) Orbitoid Foraminifera 4. Disc-shaped or button-like, with longitudinal partitions or septa Coral C. Fossils composed of segments or plates 1. Circular discs or chambers; when united form cylinder a. Tapered shell Cephalopod b. Not tapered, segments small of uniform thickness, hole in center Crinoid Stem 2. Fossil composed of many-sided plates a. Bud-shaped, 13 wedge-shaped plates Blastoid b. Cup-shaped, many curved plates branching arms Crinoid [Illustration: Plate 7 Fossil Identification Chart II BILATERAL SYMMETRY]