118 



BULLETIN 71, UNITED STATES NATIONAL MUSEUM. 



Distribution. — Specimens were found by Goes in material from 

 Albatross station D3419 in 772 fathoms, off the west coast of Mexico. 



This is a very different species from that described by Terquem from 

 the Oolite of France. The original description of that species refers 

 to a test convex on one side and concave on the other. The recent 

 species is the same on each side and truly planospiral. The aperture 



Figs. 1S1-1S5.— Ammobaculites americanus. 184. X 20. 1S5 a, broader, more flattened form; 



6, apertural view, X 15. 



varies in the recent specimens, but is usually rather elongate, and 

 the test six times as large as the fossil species described by Terquem. 



Genus PLACOPSILINA d'Orbigny, 1850. 



Placopsilina d'Orbigny, Prodr. Pal., vol. 2, 1850, p. 96. — H. B. Brady (part), 

 Rep. Voy. Challenger, Zoology, vol. 9, 1884, p. 315. 



Description. — Test attached, chambered, the* early portion close- 

 coiled, later portions uncoiling and spreading out in an irregular but 

 in general a linear series of chambers, building no floor; last portion 

 of the test may be entirely free, made up of an irregular series of 

 chambers; wall arenaceous, aperture rounded, at the end of the last 

 formed chamber. 



