MOLLUSCOIDEA — BRACHIOPODS 



203 



Fig. 85. — Atrypa reticularis Linne, from the Hamilton formation (Middle Devo- 

 nian) of New York. Natural size. A, side view showing both \ alves. B, brachial 

 valve. C, interior of brachial valve. D, interior of pedicle valve. E, mantle 

 of the living Terebratulina coreanica with the sinuses (spaces in the mantle 

 cavity) filled with eggs. The eggs have not been indicated in the mantle of the 

 pedicle valve. Beneath these sinuses roughened thickenings of the shell fre- 

 quently occur, especially in the old shells as at of figure D. a.m., adductor 

 muscle scar (in figure C it includes all the scars within the shell) ; b., brachial 

 valve; c.p., cardinal process; d.m., diductor muscle scar; la., lacuna; m.p., 

 main pallial sinus; 0., ovarian markings on shell; p., pedicle valve; p.c, cavity 

 for attachment of pedicle ; s., socket ; /., tooth. {A to D after Hall and Clarke ; 

 E after Morse.) 



1. Sketch {a) exterior of pedicle valve, {h) exterior of brachial 

 valve with umbo of pedicle valve showing, (c) interior of pedicle 

 valve. Label valves, plications, growth lines, impressions of 

 pallial sinuses, adductor and diductor muscle impressions. 



2. What function did the pallial sinuses perform? 



3. How were the growth lamellae formed? Illustrate by 

 sketch. 



Spirifer (Figs. 74, 86). Silurian to Permian. 



Shell usually wider than long, with straight hinge line. Pedi- 

 cle valve usually with high cardinal area and strong median 



