4^ HALF-AN-HOUR 



when we bear in mind its conspicuously striking aspect, and 

 its wide diffusion," " Shell spiral, equilateral, compressed laterally, 

 lenticular ; revealing only the outermost convolutions, which 

 consist of from twelve to thirty narrow, arenate, flexuose seg- 

 ments ; the anterior border of each segment prominent, smooth, 

 forming a raised septal line ; the central portion and posterior 

 border more depressed, sometimes concave ; and sculptured 

 into numerous transverse, alternate elevations and depressions, 

 which are most conspicuous near their junction with the antece- 

 dent segment." " Peripheral margin . . . usually thin and 

 angular, often with small obtuse tubercles projecting from the 

 septal ridges of a few of the posterior segments. Young shells 

 with these tubercles developed into long, pointed, transparent 

 spines projecting from each of the segments, those of the outer- 

 most convolutions being the longest and most acute. Septal 

 plane sagittate. Septal orifices numerous, arranged in a line 

 which runs close to the surface of the an- ^\ tecedent convolu- 

 tion, and forming two lateral series, thus : * \ meeting at an an- 

 gle of the periphery of the latter." This* •shows the impor- 

 tance of considering different aspects of the shells. 



Polystomella umbilicatula (PI. 21, Figs. 4, 5) is considered 

 even by Professor Williamson himself to be a very doubtful 

 species. He says : — " Some matured specimens of this shell are 

 very difficult to distinguish from young spineless varieties of I*. 

 crispa, in which latter the peripheral margin is less compressed 

 and acute than usual ; and the question of their distinctness or 

 otherwise depends upon the value we assign to the form of this 

 margin." The "septal lines are depressed; masked by the 

 crenulations furrowing the posterior border of each segment," 

 (which cover a much shorter distance of the segment,) " septal 

 plane cordate." " Mr. Hyndman, of Belfast, forwarded to me a 

 large number of specimens of this shell, obtained from the 

 stomach of a Sheldrake shot in Belfast Bay. They were 

 unmixed with any other species of Foraminifera, though along 

 with them were numerous species of Marine Entomostracous 

 Crustaceans. We can scarcely suppose that the bird had been 

 naturalist enough thus to select individuals of so minute a species 

 by way of l?onne boudic ; it is more probable that they had pre- 

 viously been devoured by some of the marine Mollusca or 

 Acalephcc^ which had subsequently fallen a prey to the feathered 

 biped. But the animal, whatever it was, obviously distinguished 

 between Polystomella and other Foraminifera. I have never 

 met with any form in such numbers, and so free from admixture 

 with other species, as to enable a discriminating feeder to fill its 

 Stomach with it. Is this a collateral testimony to the reality of 



