6Q A. J. Jukes-Browne — Clialk-pehhles on the 



sponge spicules. Of tlie larger fragments the most conspicuous are 

 pieces of Polyzoa, ?ome of them being unusually large, while mam' 

 uf the smaller aud irregular shelly fragments ai'e probably Polyzoan 

 remains. 



No. 41. This resembles the above and has about the same variety 

 of contents. The included fragments are mostly small, consisting of 

 spheres and small shell fragments with a few small I'extularia and 

 Glohigerina. There are two or three pieces of Inocermims shell 

 showing prismatic structure and some isolated prisms ; also some 

 pieces of Echinoderm plates and many fragments of Polyzoan zoaria, 

 but of sponge spicules there are very few. 



No. 35. This has a larger proportion of amorphous matrix with 

 scattered spheres and cells and a fair number of sponge spicules, 

 but not many Inoceramus prisms. Small Foramiuifera are numerous 

 with some of larger size. The larger fragments are mostly pieces of 

 Polyzoa and fragments of Echinoderms are scarce. 



No. 25. This is a similar chalk to the last, but the slice is small, 

 and the area of original material is so limited, from the extent of 

 perforation, that little can be said of it except that sponge spicules 

 and Eoraminifera are numerous. 



No. 17. This has been so much perforated that onlj^ small portions 

 of the original rock remain. It was a chalk of the same compact 

 kind, the proportion of amorphous matrix being large and all the 

 recognizable particles small. There are several Textularia and a fe,w 

 shell fragments. 



The first two of these slides (Nos. 41 and 58) and that of M. 12a 

 may be considered together, as they consist of similar material, but it 

 is on the first two that we must rely for comparative purposes, because 

 the slice of 72« is a small one. In these two slides the number 

 of fragments of the cellular zoaria of Polyzoa is a conspicuous 

 feature which cannot be exactly matched by any chalk known to 

 Mr. Hill or myself. But if the presence of these fragments is left out 

 of account the enclosing material is comparable with the chalk of two 

 difi'erent horizons in Devon and Dorset. These are the higher beds of 

 the zone of Rhynclionella Cuvieri and certain rocky beds in the zone 

 of M. cortestudinarium. 



Until we had examined slides cut from the hard nodular beds in 

 the higher part of the R. Cuvieri zone at Beer Haibour neither 

 Mr. Hill nor 1 was aware that they possessed special characters and 

 were so similar in composition to beds of a much higher horizon, 

 i.e. to certain beds of hard chalk-limestone which occur in the zone 

 of M. cortestudinarium, (1) at Annis Knob above Beer Harbour, 

 (2) at Cruxton, near Maiden Newton, and (3) near Notton in the same 

 neighbourhood. The general composition of the two sets of beds 

 is the same, there being nearly the same proportion of cells and 

 spheres distributed through the matrix, with a relatively small 

 number of fragments derived from Inocerami or Echinoderms. Both 

 contain many Eoraminifera and a variable number of sponge spicules, 

 and neither includes any glauconite grains. 



The differences are that in the rock-beds of the cortestudinarium 

 zone there is generally a larger number of the minute cavities left by 



