CLADOCHONUS × 1 STRIATOPORA × 1 LOPHOPHYLLIDIUM PROLIFERUM × 1 MICHELINIA × 1 CANINIA × 1 LOPHOPHYLLIDIUM RADICOSUM × 1 [Illustration: Plate 16] [Illustration: CRETACEOUS CORALS] CLADOPHYLLIA × 1 PARASMILIA × 1 PLEUROCORA × 1 [Illustration: TERTIARY CORALS] ENDOPACHYS × 1 ASTRHELIA × 1 FLABELLUM × 1 MICRABACIA × 2 TROCHOSMILIA × 1 In Texas one may expect to find bryozoan remains in the Pennsylvanian rocks of north-central and Trans-Pecos Texas where they are abundant in certain of the marine shales and limestones. Bryozoans may also be collected from some Cretaceous and Tertiary beds, but their remains are small and fragmental and they are easily overlooked. Bryozoans have also been found matted on the shells of fossil mollusks and other invertebrates. Phylum Brachiopoda The brachiopods are a large group of exclusively marine organisms with shells composed of two pieces called _valves_ (fig. 13). These valves are usually composed of calcareous or phosphatic material and enclose and protect the soft parts of the brachiopod animal. The soft parts are composed of muscles, the _mantle_ (which secretes the valves), digestive, respiration, reproductive, and excretory organs, and the tentacle-bearing _lophophore_. In adult life the brachiopod is attached to the sea bottom by means of a fleshy stalk called the _pedicle_ (fig. 14), and this is usually extruded through a hole (the _pedicle foramen_) which is located in the _ventral_ or _pedicle_ valve. The upturned area which is usually present on the pedicle valve is called the _beak_. The other valve, known as the _dorsal_ or _brachial_ valve, is usually the smaller of the two (fig. 13b). The two valves are opened by means of muscles, and since death results in relaxation of these muscles, fossil brachiopods are typically found with valves closed. Brachiopods vary greatly in size and shape and exhibit a wide variety of ornamentation, such as spines, ribs, nodes, and other structures. They are abundant fossils in many of the Paleozoic rocks of Texas but are relatively rare in Mesozoic and Cenozoic formations. The phylum has been divided into two subclasses, the Inarticulata and the Articulata. This classification is based upon the nature of the _hinge-line_—the edge of the shell where the two valves articulate. [Illustration: Fig. 13. Morphology and principal parts of articulate brachiopods.] a Pedicle foramen Hinge line b Pedicle valve Beak Brachial valve CLASS INARTICULATA.—