502 



FOSSIL BRACHIOPODA 



CHAP. 



dritic occlusor scars, which are rarely divisible into anterior and 

 posterior pairs. 



In Leptaena (Fig. 334) the occlusor scars (a) in the ventral 



Fig. 331. — Atrypa reticu- 

 laris. (Wenlock Lime- 

 stone.) 



Fig. 332. — Interior of the same, seen 

 from the dorsal side, showing 

 brachial spires. (After Hall.) 



valve are narrow and median, and are enclosed by a pair of 

 flabelliform divaricator impressions (d.v) ; in the dorsal valve 

 two pairs of occlusor scars (a,a^ p.a) are well marked, and ac- 

 cessory posterior occlusor scars are traceable in some specimens. 



Fig. 333. — Productus giganteus. (After Woodward.) Carboniferous Limestone. A, 

 Interior of dorsal valve. B, Interior of ventral valve. C, Transverse section 

 of valves. D, Hinge line of A: a, occlusor scars; d, divaricator scars; i, " reni- 

 form impressions"; ca, cardinal process; h, hinge line; p, brachial prominence; 

 s, cavity for spiral arms; do, dorsal valve; ve, ventral valve. 



The vascular sinuses (v-s) and genital areas are conspicuous in 

 many species of this and other genera. 



In Waldheimia (Fig. 329) a sub-umbonal " peduncular muscle " 



