GLOSSARY. 



835 



Hartshorn formation — lower Carbonic 



of Oklahoma. 

 Hastate — shaped like the head of a 



spear. 

 Hatchetigbee formation — lower Eocenic 



of Gulf coast. 

 Hawthorn formation — lower Chipolan 



(middle Oligocenic) of Florida. 

 Hayti marls — Oligocenic of Hayti. 

 Helderbergian series — lower Devonic of 



eastern North America. 

 Hemi — a prefix, meaning half. 

 Hemisepta — in some Bryozoa, short 

 plates projecting from the posterior 

 or the anterior wall (see Fig. 208, e). 

 Hepatic — pertaining to the liver. 

 Hepta — a prefix, meaning seven. 

 Hermosa formation — Carbonic of Colo- 

 rado. 

 Hesse sandstone — lower Cambric of the 



southern Appalachians. 

 Hexa — a prefix, meaning six. 

 Hickory series — middle Cambric of 



Texas. 

 Hinckley sandstone — subdivision of St. 



Croix. 

 Hinge — that on which anything turns or 

 swings. 



Hinge area — in many brachiopods, 

 the flat area bordering the hinge 

 line ; cardinal area. 

 Hinge line — the line of articulation 

 between two valves (see Fig. 218). 

 Hinge plate — in brachiopods, the two 

 expansions at the beak, within the 

 brachial valve, bounding the dental 

 sockets and medially uniting in the 

 cardinal process. In the higher 

 forms of pelecypods (Teleodesma- 

 cea), the solid internal shelly 

 growth at the beak upon which the 

 teeth are placed. 

 Hinge teeth — in many bivalve shells, 

 projections form the hinge area of 

 one valve which fit into sockets 

 upon the opposite valve, thus 

 strengthening the union of the two 

 valves. In brachiopods, the teeth 

 are present only on the pedicle 

 valve, with only sockets on the 



brachial valve. In tooth-bearing 

 pelecypod shells, both teeth and 

 sockets are present in each valve. 



Hirsute — rough with hairs. 



Hizvasee slate — lower Cambric of the 

 southern Appalachians. 



Holo — a prefix, meaning entire. 



Holochroal — in trilobites, that type of 

 compound eye in which the visual 

 area is covered by a continuous horny 

 integument, as in Calymene. 



Holotype — see type. 



Homewood sandstone — upper Kanawha 

 (lower Carbonic) of Ohio, etc. 



Homologous — having the same type of 

 structure. 



Horseiown formation — upper division 

 of the Shasta or Comanchic series of 

 California. 



Horton formation — Mississippic of 

 Nova Scotia. 



Hosselkus limestone — upper Triassic 

 of California. 



Hudson River shales — upper Cambric to 

 upper Ordovicic of Hudson Valley, 

 etc. 



Hueconian formation — Carbonic lime- 

 stone of northwest Texas. 



Huerfano formation — lower Eocenic 

 of Colorado. 



Hunton limestone — a lithologic unit in 

 Oklahoma, partly Niagaran and partly 

 Helderbergian. 



Hydaspic division — subdivision of the 

 middle Triassic. 



Hydroid — an animal belonging to the 

 class of Hydrozoa (see I., 20). 



Hydrophyton — in hydrocorallines, the 

 horny or calcareous basal structure 

 secreted by a colony (see Figs. 56, 

 57). 



Hydrospire — in blastoids, the internal 

 calcareous tubes running parallel to 

 and bounding the sides of the ambu- 

 lacra. 



Hydrotheca — in hydrozoa, the chitinous 

 cup surrounding the base of the ex- 

 panded polyp and into which it can 

 by muscular contraction withdraw for 

 protection (see Fig. 31). 



