36 



FAMILY MILIOLIDA. 



formed by the projection of the lateral borders of the mouth somewhat beyond the septum, 

 and each one is suiTOunded by a prominent annulus of shell. 



124. Internal Structure. — On examining a thin section of a typical Peneroplis, taken 

 through the median plane between the lateral surfaces (Fig. XIX), the central chamber is 



Fig. XIX. 



Section of Peneroplis through the median plane. 



seen to have the globose form which characterises the primordial segment of the Fora- 

 minifera generally ; from this first chamber a sinfjie passar/e leads to the second, which com- 

 municates in like manner by a single passage with the third, as does the third with the 

 fourth; the fourth chamber, however, communicates by ^2i?o/iassayes with the fifth, as does 

 the fifth with the sixth, and the sixth with the seventh. In the septum between the seventh 

 and the eighth, with which the second whorl may be considered as commencing, there are 

 three apertures ; and this number continues for the four consecutive partitions which divide the 

 chambers forming the next half-convolution. Then, however, commences a very remarkable 

 increase; for whilst in each of the next two partitions there nve/our passages, the numbers 

 in the four succeeding partitions which divide the chambers completing the second turn are 

 i-espectively 6, 9, 11, and 14; whilst in the last eight partitions which divide the chambers 

 of the outer half- whorl, the numbers of the apertures are respectively 14, 20, 2G, 38, 30, 3.5, 

 44, and 48. The average distance of the apertures from each other remains nearly the same 

 throughout; so that their number pretty closely corresponds with, and may be taken to 

 represent, the length of tlic septal plane which they traverse in each case ; and it is not a 

 little remarkable, that whilst this number should only increase from 1 to 4 in the first 

 convolution and a half, it should so, rapidly augment from 4 to 48 in the last half-convolution. 



12.5. As I have not been fortunate enough to obtain any other than dried specimens of 

 this organism, I have not had the opportunity of examining the structure and arrangement 

 of its soft parts. It is obvious, however, that the body of the animal will consist of a series of 

 compressed, flattened segments, progressively increasing in their transverse diameter, and 

 communicating with each other by multiple threads or " stolons" of sai'code, the number of 



