216 -TERRA XOWV KXl'i;i>lTI( iN". 



.585. Pulvinulina crassa (dOibigny). 



Roktlina cnt^.sa, d'Orliigny, 181U, L'IjV. p. o2. pi. iii, tigs. 7, 8. 

 Pulvinulina crassa, Cushman, 1910, etc., FNP. 1915, p. 58, pi. .x.wii, lig. 1. 



Stations 1-10. 32, 50 (+ T. d. F.). 



Universally distributed in the X.Z. area, frequent and well-develuped. Fossils 

 at Stations 2 and G. At the remaining Stations rare and small. 



58(3. PulvinuliiKt truHcafxIhioidcs (d"()rl)igny). 



Rotalina truncutuUnoiiks, d'Orbigiiy. 1839. FIC. p. 132, ])1. ii, fig.s. 25-27. 



,, miclidiniana, d'Orbigny, 18t0, CBP. j). .31, pi. iii, figs. 1-3. 

 Pulvinulina tiuncalulinoides, Heron-Allen and Earland, 1914. etc., FKA. 191.j. p. 716. 



Stations 1-3, 5-12, 14 (+ T. d. F., K. I.). 



The confusion arising between d"Orbigny"s two species has been treated from 

 the bibliographical aspect by :\Iillett (M., 1898, etc., FM., 1904, p. 500), but there 

 is also a zoological side which, although a point of minor importance, may 

 be worth referring to. The two species, although unquestionably zoologically 

 identical, represent two different forms of divergent structure. P. truncatulinoides, 

 clescril)ed as a recent tv'pe, represents the thin-walled specimens with deeply 

 sunk sutures and umbilical cavity. Such individuals are to l>e found in shallow- 

 water gatherings wherever the species is recorded : the texture of the shell is 

 alwavs more or less hyaline, and the surface highly papillate under a high 

 magnification. At greater depths the shell-wall thickens, the sutural depressions 

 and the umbilical recess become filled with secondary shell-growth, and the 

 test assimies the more rounded and smoother aspect of the fossil P. iiiicheliniaiut. 

 The difference between the two is a question of shell-tliickening, and no doulit 

 mdividuals of the one type pass in the process of advancing age into the 

 other. 



Our specimens illustrate this progress very well. In the shallower X.Z. 

 Stations the open truncatulinoides type predominates, the specimens are large, hanil- 

 some, thin-walled, and typical truncatulinoides. With the deeper water, especially 

 at Stations 7-9, thick-walled specimens of the micheliniami type predominate. 

 In niany of them the sutural depressions and umbilical recess are entirely obliterated. 



The best of the truncatulinoides type are at Stations 1-3 and 6, the best of the 

 micheliniana type at 7-9, 12 and 14. 



587. Pulvinulina umhonuta (Eeuss). 



Rolulina umbonata, Reuss, 1851. FSUB. j). 75. pi. v, figs. 35, n-c. 

 Pulvinulina ,, Cushman. 1910, etc., FNP. 1915, p. 60, pi. xxvii, fig. 2. 



Stations 8-12, 16, 17, 36. 



Rare; the best at Stations 10-12 and 17. 



