I c - 



ture which is developed only near the antero-ventral margin. 



Y. solenoides Ball (l), a recent species from the Gulf of Ke:ico, 



(1). 3nll. ITus. Oompt. Zool., Harvard, vol. 9, p. 127, 1381; 

 idem, vol. 12, p. 248, r)l. 9, figs. 2, 2a, 1886. 



has the same general facies, hut is more elongate, ttie length 

 heing slightly more than twice the altit^i'^.e, the p^Jo-ne of the 

 anterior dorsal margin is less steep, the posterior dorsal ma.rgin 

 Joins the lateral mar?<in by a gentle curve, instead of a sharp 

 angle, the posterior end is more symmetrically arcuate and the ven- 

 tral margin less ciirved. 



Occurrence .- Upncr Oligccene : Santo Domiupro (Oahh, 187?);. 

 Lo^rer Miocene: Bowden heds, Bowden, Jamaica (Dall, 



1905). 



