PLATE XXI Continued. 



Page. 

 LINGULA ELDERI Ill 



Fig. 18. Outline of the interior of the dorsal valve, showing the muscular and vascular 

 markings: 



d. Divaricator muscular scar. 

 a d. Adjuster muscular scars. 

 p a. Posterior addiictor scars. 

 a a. Anterior adductor scars. 

 xx. Track of advance of the muscular scars. 



s. Great pallial sinuses. 

 p s. Posterior course of the latter. 

 o. Inner ramifications of the sinuses. 

 (After Whitfield.) 



LINGULA. WHITEI 109 



Fig. 19. Outline of the figure of this species on plate xiii, fig. 5. The corresponding parts 

 are lettered, as in fig. 18. 



LINGULA AFFINIS Ill 



Fig. 20. Dorsal valve, reduced, after Hancock's figure. Lettering, the same as in figs. 18 

 and 19. 



