24 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



and Stauractinella, are both deep-sea sponges, but are also found in 

 shallow water. Figures 24, 25, 2G, 30, and 31 are similar to deep-sea 

 recent forms figured by Carter, while the Mouactiuellid sponges are 

 shallow water forms. Dr. Hinde concludes that the sponges in the 

 Horseford flint " do not show conclusively the depth of the water of the 

 deposition." 1 



In the Challenger Reports, Volume on Deep-Sea Deposits, Mr. Murray 

 takes the position that the chalk was not the same as the present 

 globigerina ooze, because the species of Foraminifera in the chalk are 

 principally shallow water forms. However, the appearance of the 

 nodules so seldom in the cretaceous formations seems to indicate a very 

 peculiar combination of circumstances which existed but once in a great 

 cycle of changes. From its proximity to known shore lines, we may 

 judge that this formation was not in the deepest sea, yet from the forms 

 of animal life preserved in it we may conclude that it was beyond the 

 continental shelf, in water deep enough to secure the conditions necessary 

 for long periods of time. 



1 Fossil Sponge Spicules of the Upper Chalk, p. 76. 



