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PROCEEDINGS OF THE COTTESWOLD CLUB 213 



I have one diatom which most resembles Bacillaria. It is 

 quite worth while, however, to bear in mind, when ex- 

 amining chalk, that diatoms do occur in it. 



The Polyzoa of the Chalk are numerous and interesting, 

 and, as a rule, are in a splendid state of preservation. They 

 all ap[)ear to belong to the order Infundibulata, sub-order 

 Cyclostomata, i.e., those in which the cells have a simple, 

 round mouth. 1 have a good many forms mounted ; but 

 as I have not been able to get access to any work upon 

 the Chalk Polyzoa, I have not been able to gather much 

 information respecting them. Beautiful specimens of 

 Diastopora, Alecto, and other parasitic forms may fre- 

 quently be found incrusting the shells of the commoner 

 Echinoderms, such as Micraster and Ananchytes ; and by 

 washing the soft chalk which is found in the external 

 hollows of flints many fragments of the erect-growing 

 forms ma)' be secured. Of the many specimens ot 

 Polyzoa which I have procured from the Chalk, not a 

 single one has any appearance of having possessed the 

 peculiar appendage called the " avicularia," or bird's-head 

 process ; and only one solitary example has vibracula. 

 This is a somewhat singular circumstance, as in the 

 Polyzoa of the Crag, and in the majority of living species, 

 either avicularia or vibracula are present, and in some 

 both occur. In most of the Chalk Polyzoa a few of the 

 cells are found to be almost closed by a calcareous 

 diaphragm, or extra growth extending inwards from the 

 edge of the mouth of the cell, and having a very small 

 opening in the centre. This appears to be in some 

 way connected with the process of sexual reproduction. 



I have already referred to flint in speaking of the 

 sponges ; but sponge spicules are not the only interesting 

 objects to be found therein. In some specimens very per- 

 fect casts of the interior of the shells of the Foraminifera 

 may be found, showing in the most complete manner the 



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