1 64 BuivLKTiN 29 328 



Area umbonata Sheldon, Palseont. Amer., vol. 1, p. 8, pi. 1, figs. 12-17, 

 1916. 



Our fossil shell is exactly like the recent from the Monte 

 Cristi beach but smaller. The species occurs in the Oligocene of 

 Florida and in the Antillean Pleistocene and recent faunas, but 

 has not been found at Bowden. 



Locality. — (Exp'd '16) Zone H, Rio Can a at Caimito. 



Area lomasdesamba, n. sp. 

 Plate 30, Figure 12, 



Shell resembling in general form the young of A. occidentalism 

 but the ribs are more uniform and more nodulous. The whole 

 plan of sculpture is more elegant. A . occidentalis characteristic- 

 ally has a nearly smooth band (with a group of fine threads) 

 over the umbonal ridge, and another similar band along the pos- 

 terior dorsal margin; between these bands is a pronounced sulcus 

 containing a few normal ribs. The specimen now described 

 shows only very slight development of bands, and the sulcus is 

 much less pronounced. Length of shell 32, altitude 14, thick- 

 ness of both valves 14 mm. 



The Chipola analogue is A. paratina Dall, which is smaller, 

 with much finer ribbing. 



Locality. — (Exp'd '16) Samba Hills, altitude approximately 

 540 feet. 



Area yaquensis, n. sp. 



Plate 30, Figure 14 



We have about sixteen valves of a minute, true Ark with- 

 out special characters, but apparently not the young of any 

 other species. It is not alate, but is obliquely truncate poster- 

 iorly, and there is no differentiation of the ribs over the rounded, 

 not angular, umbonal ridge. Exteriorly the shell somewhat re- 

 sembles a Scapharca. Perhaps the shell is not quite mature, 

 -ince the margin is still crenulate. Length 9, altitude 4.75 mm 



Printed April 9, 1917 



