MALACOZOA. CEPHALOPODA. FORAM1NIFERA. 317 



4. Polystomella umlilicatula. Umbilicated Polystomella. 



Shell discoid, compressed, with the sides nearly flat, 

 the margin rounded ; the cells of the last turn ten or 

 twelve, curved, broadly convex, smootliish, glossy, the 

 interstices depressed, granulato-sulcate ; the centres de- 

 pressed, little concave, somewhat granulated ; the end 

 of the last cell large, cordate, somewhat convex. Urn- 

 bilicutulus, small and with a conspicuous umbilicus. 



Shell roundish, thin, with the margin rounded and lobulate; 

 the centres slightly depressed, rather large, nearly flat, granu- 

 lated ; the last turn with ten or twelve cells, which area little 

 curved, convex, smooth, and glossy, sometimes minutely granu- 

 lated, the interstices sunk, and granulated; the end of the 

 last turn large, cordate, embracing the previous turn, and 

 having a convex granulated cover, near the centre of which is 

 a minute pore; the colour hyaline-white, with the dissepi- 

 ments opaque-white, the centre opaque. Diameter about the 

 twenty- fifth of an inch. 



Found by me in December, 1 842, in shell sand from Cruden 

 Bay, sent by Mr. Alexander Murray ; and on the 7th January, 

 1843, common, on Terebellae, on the beach at Aberdeen. 



Nautilus spiralis umbilicatus, geniculis sulcatis. Walker, Test. 

 M in. Rar. PI. 3. f. 69. Nautilus umbilicatulus. Mont. Test. Brit. 

 I'M ; Supplt. 78. PI. 18.f. 1. Nautilus umbilicatulus. Flem. Brit. 

 Anini. ^i). 



5. Polystomclla nautilina. Nautiline Polystomella. 



Shell nautiliform, with the sides somewhat convex, 

 the margin rounded, the cells of the last turn about ten 

 or twelve, little convex, narrow, smooth, glossy, but 

 granulated toward the umbilicus, which is small, the 

 interstices depressed, curved, and somewhat striate ; the 

 end of the last cell large, cordate, nearly flat, with two 

 series of pores. Nautilinus, like a Nautilus. 



Shell somewhat of the form of Nautilus Pompilius, having 

 tbi' last turn of about ten cells, which gradually enlarge, until 

 near the mouth, when they increase in size much more rapidly; 

 the- sides somewhat convex, the margin rounded; the dissepi- 

 ments a little sunk and curved; the cells convex, and glossy, 

 unless toward the small, depressed, distinct umbilici, where 



