071 the Organic Composition of Chalk and Chalk Marl. 387 



alone), may be seen a pretty mosaic of well-preserved, moss- 

 coral animalcules, but which are invisible to the naked eye. 

 And thus our natural vision receives from such a surface the 

 impression of the purest white, little deeming that it contains 

 the bodies of millions of self-existing beings, of varied and 

 beautiful forms, more or less closely crowded together (as in 

 Plate IV., where the subjects are magnified 300 times). 



Explanation of the Plates and Tabular Vieno. 



The Memoir is accompanied by four Plates*, presented with 

 the view of facilitating a comparison between the organic re- 

 lations of minute fossil bodies invisible to the naked eye, and 

 those of still living bodies visible to the naked eye. 



Thus the first three Plates exhibit recent small bodies natu- 

 rally visible, with which the naturally invisible forms of the 

 fourth Plate may be readily associated. 



The first three Plates serve also to elucidate the true nature 

 of the Polythalamia (hitherto mistaken), showing their greater 

 aflfinity to the Bryozoa (Flustra) than to all other animal 

 forms, and in particular the great difference there is between 

 them and Cephalopods and Infusoria, They represent partly 

 the unfolded, soft, external parts of living subjects, and partly 

 dead, naked bo(hes, artificially divested of their calcareous 

 shell, and not hitherto figured. 



Lastly, these first three Plates serve to convey a view, ac- 

 cording to some of their principal divisions, of the structure 

 of the whole group of forms occurring in Polythalamia, and 

 in particular to illustrate their frequent assemblage in families, 

 or Polyparies, as they are termed. Plate I. contains simple 

 forms ; Plates II. and III. composite or family forms, Poly- 

 paries; of which Plate II. contains family forms assembled in 

 single rows, and Plate III. family forms arranged in many rows. 



It, as already observed, we examine a wall or paper whitened 

 with finely levigated chalk, or a glazed visiting-card not coated 

 with white lead alone, but also with chalk, they would appear, 

 when magnified 300 times, more or less rich in subjects, as 

 represented in Plate IV. 



Plate I. contains si7nple recent Foli/thalamia from the sea- 

 sand of Rimini. Fig. 1. Rotalia Beccarii; the shell only was 

 known, but the figures show also the form of the animal when 

 deprived of its shell by an acid, the form of both being the 

 same. Fig. 2. Margitndina Haphamis {Nodosaria llapJiamis, 

 Nautilus llaphanus prionmi), also very common at Rimini 

 and other Italian coasts, and which had hitherto been errone- 

 ously ranked with Orthocera. 



Plate II. contains Polyparies of recent Polythalamia assem- 



* These plates do not accompany Mr. Weaver's paper. 

 2 C2 



