PLATE XXI—Continued. 
Page. 
LINGULA. ELDER. o5sc0 5255/5250 che stise ee Lae nled eee ae ae eee eee eee oe ee eee 111 
Fig. 18, Outline of the interior of the dorsal valve, showing the muscular and vascular 
markings: 
d. Divaricator muscular scar. 
ad, Adjustor muscular scars, 
pa. Posterior adductor scars. 
aa. Anterior adductor scars, 
xa. Track of advance of the muscular scars. 
s. Great pallial sinuses. 
ps. Posterior course of the latter. 
o. Inner ramifications of the sinuses. 
(After Whitfield. ) 
More ope’ WA RGU AS Boos coocnd CESoneCHE Saoscesesnecn sec Sac ese ORO ChED Ssescocceoeonert backed] 109 
Fig. 19. Outline of the figure of this species on plate xiii, fig. 5. The corresponding parts 
are lettered, as in fig. 18. F; 
TUINGUDAVAREUNIS: cose sieasisite ee clare coe an siete arlene ra eee ena Re a ere eee SBD ECA SOE ME cone aoe 111 
Fig. 20. Dorsal valve, reduced, after Hancock’s figure. Lettering, the same as in figs. 18 
and 19. 
