13-1 J. J. LISTER. 



some cases there is an indication of a globular swelling near the 

 apex of the cone, and this might be considered to be the second 

 chamber, the remainder of the cone being the third. The suc- 

 ceeding chambers gradually increase in size, but the cog-like 

 " retral processes " (see fig. 13) characteristic of the genus do not 

 appear for some distance along the series of chambers. 



The spire in which the first few chambers are disposed is 

 often not flat, as in the succeeding chambers, but helicoid. When 

 this is the case, the direction of the spire is sometimes dextro- 

 tropic and sometimes leiotropic. 



Though the size attained is not larger than that of the 

 megalospheric form, the number of chambers in specimens of 

 the two forms of equal size is greater in the microspheric. This 

 is owing to the fact that in this form the central region is occu- 

 pied by small chambers which gradually diminish in size to the 

 microsphere, while in the megalospheric form, a single large 

 chamber, the megalosphere, occupies the centre. 



The smallest specimen I have seen (fig. 7) has twenty 

 chambers, and measures 230 /t across the short diameter of the 

 spire of chambers ; one of the largest has forty-seven chambers, 

 and measures 800 fi. 



Nuclei. — Microspheric individuals have many nuclei. They 

 are distributed through many chambers, beginning at one of 

 the internal chambers, and extending some distance beyond the 

 middle of the series, counting from the microsphere to the 

 terminal chamber. Thus, in a specimen with twenty-nine 

 chambers there are twenty-eight nuclei extending from the 

 fourth to the twenty-third. In one with forty-two chambers, 

 there are forty-four nuclei extending from the thirteenth to the 

 thirty-first. 



There may be one, two, or as many as six nuclei present in 

 one chamber, and on the other hand a chamber may be free 

 from nuclei while the adjoining chambers contain them. I 

 have never seen the nuclei extending into the terminal 

 chambers. 



The nuclei are generally of a round or oval shape. In 

 nearly every case they are small in the inner chambers, and 



