FOEAMINIFERA OF THE WEST OF SCOTLAND. 283 



321. Polystomella arctica, Parker & Jones. 



Polystomella arctica, Parker & Jones, MS. ; Brady, 1864, RFS. p. 471, pi. xlviii. fig. 18. 

 Brady, 1884, FC. p. 735, pi. ex. figs. 2-5. 



8 Stations. 



Rare, and the specimens few in number, rather small, and generally worn. The best 

 specimens were at Stn. 22. 



322. Polystomella macella (Fichtel & Moll). 



Nautilus macellus, Fichtel & Moll, 1798, TM. p. 66, pi. x. figs. e-g. 

 Polystomella macella, Brady, 1884, FC. p. 737, pi. ex. figs. 8, 9, 11, & ? 10. 



18 Stations. 



Widely distributed, but never very abundant, the best at Stns. 3, 4, and 17. The 

 chief variation lies in the relative depression of the septal lines, which in some cases are 

 so depressed as to give a turgid character to the chambers. These turgid specimens 

 are, as a rule, characterized by a granular deposit over the shell-substance. At Stns. 6 

 and 8 the specimens were intermediate between P. macella and P. crispa. 



323. Polystomella crispa (Linne). 



Nautilus crispus, Linne, 1767, SN. p. 1162. No. 275. 

 Pult/stomella crhpa, Brady, 1884, FC. p. 736, pi. ex. figs. 6, 7. 



21 Stations. 



Almost universally distributed, but never common. The specimens are, as a rule, 

 large and handsome and of the compressed type. At several Stns., notably at Stns. 4 

 and 17, the marginal spines persist to an advanced or even mature stage (see H.-A. 

 & E. 1913, 01. p. 146, pi. xiii. fig. 14). Distorted specimens occur at Stns. 5, 11, and 

 notably Stn. 15, usually due to fission of tbe protoplasm separating into two distinct 

 shells at about half the growth, the subsequent growth being continued on two distinct 

 planes. 



Subfamily Nummulitin^e. 

 Operculina, d'Orbigny. 



324. Operculina ammonoides (Gronovius). 



Nautilus ammonoides, Gronovius, 1781, ZG. p. 282. No. 1220, pi. xix. (fasc. iii. tab. 2) figs. 5, 6. 

 Operculina ammonoides, Brady, 1884, FC. p. 745, pi. cxii. figs. 1, 2. 



20 Stations. 



Almost universally distributed, often very common, the best specimens at Stns. 4<, 

 11, and 14. Variation is almost entirely dependent on the degree of limbation of the 

 sutures, which at some Stns. is very marked and striking. Distorted or wild-growing 

 forms occur at Stns. 19, 20, and 21. At Stn. 19 there is a tendency to an inflation of the 

 later chambers. 



