NIAGARA FALLS AND VICINITY 269 



intrathecal — within the theca; endothecal 



introverted — turned apex to apex; applied to the spirals of brachiopods 



involute — rolled up, as a Nautilus shell 



joints: — component segments of the stem of a crinoid 



jugum — yoke-like connection between the two parts of the brachidium of 

 a brachiopod 



keel — strong central carina or ridge (Taeniopora) 



lacrymiform — tear-form; drop shaped — pear shaped, but without the lateral 

 contractions 



lamellar — disposed in lamellae or layers 



lamellibranch — leaf-gilled, the class of molluska with bivalved shell, to which 

 the oyster and clam belong; pelecypod 



lamelliform — having the form of a leaf or lamella 



lamellose — made up of lamellae 



lamina — a thin plate or scale 



lateral gemmation — a budding from the sides, as in some corals 



lateral teeth — ridge-like projections on either side of the beak, in the in- 

 terior of lamellibranch shells 



laviformia — primitive order of crinoids 



ligament — external structure for opening the valves in the pelecypoda 



limb — lateral area or marginal band of the cephalon of trilobites on either 

 side of the glabella, corresponding to a pleuron of the thoracic region 



lines of growth — lines marking the periodic increase in size, in shells 



linguiform — tongue-shaped 



linguloid — tongue-shaped; like Lingula 



lip — margins of the aperture of univalve shell 



listrium — depressed area surrounding the pedicle opening in the pedicle 

 valve of Orbiculoidea and other discinoid brachiopods 



lithic — pertaining to stone 



living chamber — the last chamber in the shell of a cephalopod, which is 

 occupied by the animal 



lobes — backward bending portions of the suture of cephalopod shells 



lophophore — ciliated or tentaculated, oral disk of bryozoa; the oral disk 

 and brachia of brachiopods 



lunarium — more or less thickened portion of the posterior wall of the cell 

 in many paleozoic bryozoa, which is lunate or curved to a shorter 

 radius, and usually projects above the plane of the cell aperture 



lunule — depression in front of the beak of pelecypod shells 



macerate — softening and disintegrating by immersion in water 



macrocorallites — the larger corallites in a compound corallum 



maculae — irregular, usually depressed, areas on the celluliferous face of a 



bryozoan frond, which are free from cells, or otherwise differentiated 

 mandibles — first upper or outer pair of jaws of Crustacea and insects 



