224 



NEW YORK STATE MUSEUM 



on the morphology and to some degree phylogeny of this genus. This lar- 

 val shell in the adult condition of Lunulicardium clymeniae, lies 

 with its apex or primitive beak directed downward or toward the postlateral 



Fig. 2, 3 Umbonal parts of L u n u 1 i c a rdi urn clymeniae, showing triangular area, projecting plications and sical 



surface. 



extremity of the adult shell, so that the original "posterior" extremity of 

 the larval shell actually lies at and constitutes the beak of the adult. This 

 relation is shown in the accompanying figures. The shell has in growth 



- -Fig. 4-6 The prodissoconch of Lunulicardium clymeniae viewed in three attitudes, to show its relation to the 

 mature shell. The apex is directed obliquely backward and the posterior end of the larval shell is the umbonal point of the 

 adult. 



actually twisted with reference to the animal, and the axial line which we 

 have marked o-a has apparently traveled through a large angle to reach 

 the corresponding position in the adult, o-a [see fig. 7]. 



