564: Notices of Memoirs — W. H. DaWs Molluscan Report. 



pressure. The phrase " chemical action" is used, I think, a little 

 too freely in many quarters, by people who make no pretensions to 

 be considered chemists, as a sort of limbo to which to relegate points 

 in petrology which they do not wish to explain. 



May I add here a word of congratulation to Mr. W. M. Hutchings 

 on his most valuable researches ' in the fire-clays of Northumberland ? 

 He has given us a mass of facts which prove in a concrete instance, 

 what I have contended for on general grounds (e.g. op. cit. pp. 53, 

 93 2 ) ; and has simply "ripped up " the fallacy, post hoc ergo propter 

 hoc, which underlies the assumption so often made, that the develop- 

 ment of secondary minerals in cleaved slates and similar rocks is 

 due to " dynamic-metamorphism"; since he has demonstrated their 

 presence, to a large extent as the result of the ever-active laws of 

 chemical change (aided by aqueous diffusion) in a rock which has 

 undergone no dynamic metamorphism whatever. 



IsTOTICES O^ 1 IMIIEIMIOIIRS- 



I. — Scientific Eesults of Explorations by the U. S. Fish 

 Commission Steamer Albatross. No. VII. Preliminary Report 

 on the Collection of Mollusca and Brachiopoda obtained in 

 1887-88. By William Healey Dall, A.M. Proceedings of 

 the National Museum, Vol. XII. No. 773. 



THOUGH the greater part of this Report is devoted to a de- 

 scription of the species obtained, there are some introductory 

 remarks which should not be overlooked by geologists on the 

 conditions of life in the deep sea and on the nature of deep-sea 

 deposits. Some of the most interesting of these notes relate to 

 the " Archibenthal Region," as Mr. Dall terms the area which lies 

 below the limit of Algas and above the Abyssal Region. In this 

 region "the action of erosion and solution .... seems less potent 

 than in either the shallower or the deeper parts of the sea. In the 

 shallower parts the excess of motion, in the deeps the excess of the 

 eroding agent, may account for this." Some of the banks in these 

 depths are formed in a way which should be noted, as perhaps 

 accounting for the large quantities of broken shells often found in 

 fine deposits which show little sign of currents. Mr. Dall speaks 

 of " the habit of certain fishes, which exist in vast numbers, of 

 frequenting certain areas where they eject the broken shells .... 

 which they have cracked, swallowed, and cleansed of their soft 

 tissues by digestion Now, in examining critically large quan- 

 tities dredged from the bottom, I have found the material from 

 certain areas almost entirely composed of these ejectamenta." 



In some 16 pp. of ' general considerations ' on the Pelecypoda. Mr. 

 Dall gives an account of the genesis of the molluscan hinge, and 

 groups the bivalves into three orders, Anomalodesmacea, Prionodes- 

 niacea, and Teleodesmacea. It is impossible in a short abstract to 



1 Vide Geol. Mag. for June and July 1890. 



2 See also Appendix ii. Note T. 



