Figure 34.— Interiors of valves of Obolus and Lingula. 

 Obolus apollinis quenstedti Mickwitz. After Mickwitz [1S96, figs. 6a-b, p. 79]. A, Ventral valve; B, dorsal valve. 



I. Splanchnocoele. 

 TI. Bracliiocoele. 

 III. Pleiiroccele. 

 a. Pedicle furrow. 

 I). Parietal band. 

 c. Heart-shaped pit. 



d. Canals of principal vessels. 



e. Peripheral vascular canal. 



f. Secondary vascular canals. 



g. Umbonal muscle, 

 h. Central muscles. 



i. Transmedian muscles. 



j. Anterior lateral muscles. 

 k. Middle lateral muscles. 



1. Outside lateral muscles, 

 m. Median septum, 

 n. Lateral septa, 

 o. Sinus. 



p. Median ridge. 



q. Hornlike projections. 



s. Pedicle muscle. 



u. Flexure lines of area lamellae. 



Lingula anatlna Bruguifere. After King [1873, PI. II, figs. 1 and 2]. C, Ventral valve; D, dorsal valve. 



b. Parietal band which bounds 

 the splanchnocoelic chamber 

 in both valves. 



'C. Liver, 



•d. Genitalia. 



e. Intestine. 



f. Termination of intestine. 

 ,g. Umbonal muscle. 



374 



h. Central muscles. 



i. Transmedian muscles. 



j. Anterior lateral muscles. 

 k. Middle lateral muscles. 



1. Outside lateral muscles. 

 m. Plemocoeles. 



n. Vessels of pleurocoeles (exag- 

 gerated). 



Primary vessels of bracliio- 

 coele. 



Secondary vessels of brachio- 

 ccele (those passing from the 

 inner side of the primaries 

 may be called ingoers and 

 those on the outer side out- 

 goers). 



u. Setal band (the pedicle is not 

 represented, as it would ob- 

 scure the continuation of this 

 band in the rostral region). 



V. Inner edge of setal band (an- 

 swering also to the line ot 

 vascular constriction). 



w. Outer edge of setal band. 



X. SetEe. 



