NIAGARA FALLS AND VICINITY 267 



escutcheon — depression behind the beak of the pelecypod shell 



exfoliate — peeling off 



exothecal — outside of the theca of corals 



explanate — spread out in a flat surface 



extrathecal — outside of the theca of corals 



extroverted — turned base to base; applied to spirals of brachiopods 



facetted — having facets or numerous faces as the eye of an insect, etc. 



facial sutures — sutures in the cephalon of trilobites which separate the free 



from the fixed cheeks 

 facies — local characteristics 

 falcate — curved like a scythe or sickle 

 fasciculate — clustered 

 fathom — a measure of length equaling 6 feet used chiefly for depths of the 



sea 

 fenestrule — open spaces between the branches and dissepiments of a fene- 



stella frond 

 filament — a fine thread or fiber 

 fimbriae — a fringe 

 fixed cheek — that part of the cephalon of a trilobite which lies between the 



glabella and the facial suture 

 fission — the act of splitting or cleaving into parts 

 flabellate — fan-shaped 

 flange — a projecting rim 

 flexibilia — an order of crinoids characterized by the loose jointing of the 



plates of the calyx 

 fold — the central elevation of the valve, usually the brachial of a 



brachiopod 

 foliate — leaf-like; in the form of a thin leaf-like expansion 

 foramen — an opening or pore; specifically the opening for the pedicle in the 



pedicle valve of the brachiopoda 

 fossula — groove in the calyx of a coral, usually due to the abortion of a 



septum 

 free cheeks — lateral portions of the cephalon of trilobites separated off by 



the facial sutures 

 frond — foliaceous or leaf-like expansion of the skeleton of bryozoa and 



other organisms 

 fruticulose — resembling a small shrub 

 fucoid — a seaweed, particularly of the type similar to the modern Fucus, or 



rockweed 

 galeate — with a helmet-like covering 

 gastric — pertaining to the stomach 



genal angles — posterior .lateral angles of the free cheeks of trilobites 

 genal spines — posterior prolongations, or spines, of the free cheeks of 



trilobites 

 geode — a hollow concretion usually lined with crystals, but also filled com- 

 pletely with foreign mineral matter 



