(0 78 Palseontologia Sinica Ser B. 



sections; sections through the centers of two opposite beads would show the greatest 

 amount of thickening, while sections through the depression between the beads would 

 show the least, others falling between these. 



In the majority of specimens the septa show secondary thickening, either on 

 one or on both sides. This is however seldom if ever as extensive as in A. tani. In 

 some cases, indeed, it is scarcely developed, or is strongly developed on one side only, 

 as in the type figured by Freeh (loc. cit. Plate 2 fig. 4a). The bowl-shaped depression 

 which is formed around the siphuncle by the abrupt oblique truncation of the deposit 

 near the siphuncle, in such species as A. tani and some others, is seldom developed. 

 I have not seen it in perfection in any specimen of this species, though it occurs in 

 individual septa. Not infrequently the deposit widens towards the siphuncle, and comes 

 in close contact with it. One or two pseudosepta are commonly present in each camera 

 characterized by such deposit. One may divide the deposit into two parts, and the other 

 terminate it, after which there is an interval represented by an empty space (filled, 

 except in weathered specimens, by the rock matrix *) and then a new septum follows. 



In some cases the stereoplasm is included between the septum and a pseudosep- 

 tum next in front (see fig. Plate IX). Again there may be a slight deposit of 

 stereoplasm both on the upper and under sides of the septum, but this is generally 

 irregular, especially on the under side, as if the septum had been broken. Thickening 

 by stereoplasm on both sides of the septa is indicated in Freeh's figure of the type, but I 

 have not seen any specimen in which the thickening is as regular as is shown on the 

 right side of his figure. A fragment which I refer to this species (Plate IX, fig. 5) 

 has the cameras nearly filled with stereoplasm, the septa appearing out of position, ending 

 apparently against the nummuli. This would give the appearance of Freeh's figure, if we 

 assume that the septa are pseudosepta, and that true septa occur in the midst of the 

 stereoplasm deposit. Of this there is however no indication. In fact, the septa are 

 strongly bent backwards, so as to rest for a space against the upper or frontal surface of 

 the next preceding nummulus. If a deposit of stereoplasm exists on the under side of the 

 septum it could hardly be explained otherwise, than by assuming its formation to have 

 taken place after the formation of the septum, in which case there must have remained 

 some organic connection between the camera and the animal. 



* It is a noteworthy fact, that the eriginally empty portions of the earners? are almost always filled with the 

 rock matrix (generally in our specimens a calcilutytej in which the shell as a whole is embedded. It does not seem likely 

 that the lime-mud, fine though it was, could filter through the " endosiphuncle " and the radiating tubules into these 

 earners? (no mud-filled tubules have been observed), and we therefore must conclude that it entered through fractures in 

 the outer shell, fprmd no doubt by crushing after burial. In some cages the shell is seen to have been worn away before 

 final burial, and in such specimens of course all empty spaces were filled by the lime-mud, and in some cases even other 

 foreign substances, such as fragments of other fossils, are enclosed. 



