294 CAMBRIAN BRACHIOPODA. 



EpJiebic. — Designating the mature shell. 



False area. — See Cardinal area. 



Flexure line. — See Cardinal area. 



Foramen. — A small circular passage through the deltidium, either below or at the apex of 

 the ventral valve. Sometimes the foramen encroaches by pedicle abrasion on the umbo of the 

 ventral valve. (See p. 314.) 



Foraminal tube. — The pedicle opening through the ventral valve of neotrematous genera. 

 (See PL LVIII, fig. 5b.) 



Genital marlcings. — Radial markings or pits within the posterior portion of the visceral 

 space, mdicating the position and extent of the genitals. 



Gerontic. — Designating old age. It is indicated in the ontogeny of many species of brachio- 

 pods by extreme thickness of the valves, obesity, or by numerous crowded growth lines near 

 the anterior margin, a condition which sometimes produces truncation and absence of strise 

 at the margin. (See p. 315.) 



Heart-sliaped cavity. — Central depressed portion of visceral area (Mickwitz). (See PI. 

 VII, figs. 9, 11, and 12 at x; also figs. 1, 2, and 8.) 



Hinge line. — The line along which articulation takes place. Also sometimes developed 

 among inarticulate brachiopods. 



Inarticulate brachiopods. — In the orders Atremata and Neotremata the valves do not, as 

 a rule, articulate by means of teeth and sockets, as is the case in the articulate orders Pro- 

 tremata and Telotremata. 



Lateral areas. — That portion of the shell on each side of the central axis. 



Listrium. — In some Neotremata a plate closing the progressive track of the pedicle opening 

 or pedicle cleft posterior to the apex of the ventral valve. (See p. 306.) 



Longitudinal axis. — A median line tlirough the shell from the beak to the opposite margin. 



Median septum. — An internal vertical plate commonly developed along the longitudinal 

 axis and between the muscles of the ventral valve. Sometimes there is also a dorsal median 

 septum. Lateral septa are rarely developed. 



Middle lateral muscle scar. — See Outside and middle lateral muscles. 



Neanic. — Designating youthfulness, or the stage in which specific characters begin to 

 develop. 



Neotremata. — Circular or oval, more or less cone shaped, inarticulate calcareophosphatic 

 brachiopods with the pedicle opening restricted throughout life to the ventral valve. For a 

 more detailed description see "Classification of Cambrian Brachiopoda," page 323. 



Nepionic. — Designating the smooth shell stage succeeding the protegulum. 



Outside and middle lateral (protractor) muscles. — In the ObolidiB one pair has the ventral 

 ends fastened at the anterior extremity of the visceral area, extending backward and inserted 

 near the lateral margin of the dorsal valve, outside the transmedians. A second pair originates 

 just behind the centrals of the ventral valve and is inserted posterior to the first pair. These 

 muscles draw the dorsal valve forward. 



Parietal band. — The point of attachment of the muscular wall surrounding the visceral 

 area. 



Pedicle. — The fiexible muscular organ of the ventral valve by means of which brachiopods 

 may be attached to extraneous objects. 



Pedicle furrow. — The external furrow adjoining the foramen or pedicle opening in certain 

 neotrematous genera. (See PI. LXXXIII, figs. 1 and 2 ; PL LXXXIV, figs. 1 and 5c.) 



Pedicle groove. — The median groove on the cardmal areas of the valves, formed by the pedicle 

 extending through the posterior margin of the valves when they were closed. 



Pedicle muscles. — In the Protremata and Telotremata one pair originates on the ventral 

 valve at points just outside and behind the diductors and another on the dorsal valve behind 

 the posterior centrals, while the opposite ends of both are attached to the pedicle. Besides these 

 there is an unpaired muscle lying at the base of the pedicle, attaching it closely to the ventral 

 valve. 



