534 Correspondence — Mr. E, Fielding, 



The condition of these could be best explained by an illustration 

 which, if desired, I shall be happy to draw. — Edward Fielding. 



London, 22nd October, 18G8. 



Note. — We feel sure that Dr. Duncan will be glad to have attention called to his 

 interesting paper on Heterophyllia, and also to have the testimony of so able an artist 

 as Mr. Fielding to the accuracy of Mr. De Wilde's delineations. We are quite 

 certain that he will himself be only too happy to re-examine a point upon which, 

 possibly, something more may be determined. 



Mr. Young, in his paper (Gtegl. Mag., October, 1868, p. 451), says, if a coral had 

 spines articulated at their bases, upon rounded tubercles, such a structure would be 

 quite an anomaly in a zoophyte. 



We must beg Mr. Yoimg not to reject a discovery because it is anomalous. Palseo- 

 zoic life -structures present many strange features. Whether we accept or reject the 

 doctrines of evolution and descent with modification, we cannot fail to observe 

 many forms which present what Prof. Owen has aptly termed " a more generalized 

 type of structure," than representatives of the class now existing.^ 



In illustration of this we would refer to an admirable paper wliich appeared in this 

 Magazine in 1866, Vol. III., p. 306, On Zoantharia Rugosa, by Dr. Lindstrom. 

 (with a Plate). The author shows that this remarkable group of corals (before re- 

 ferred in part to Corals, and in part to Brachiopoda) were all furnished with an 

 operculum or valve ! Surely this is a still more wonderful and anomalous structure 

 in a coral, than the lateral spines on Heterophyllia mirabilis. 



Nor should it be assumed that an appearance like that of a ball-and-socket joint 

 necesmrily implies movement ; for we have among the Echinodermata (both fossil and 

 recent) immoveable and moveable spines, the former of which, when removed, leave an 

 appearance similar to that of the latter. Such structures — like rudimentary appen- 

 dages — seem rather to indicate what the earlier state of the creature may have been, 

 than what it now is. 



Among the Crustacea, spines exist, which, like the immoveable spines of some Echi- 

 noderms, present an articular surface, not a fracture, when they are removed {e.g. the 

 spines on the rostrum of Palmnon and on the margin of the thorax of limulus). — 

 Edit. Geol. Mag. 



SYNCHRONOIJS AGE OF THE GKAYS AND EEITH BRIGKEARTHS. 



Sir, — In reference to the Brick-earth of Erith and Crayford, which, 

 in my paper on the Post-glacial structure of the South-east of Eng- 

 land, published in the 23rd volume of the Journal of the Geological 

 Society, I regarded as being distinct from that at Grays, and of an 

 age anterior to the main sheet of the Thames gravel, I shall feel 

 obliged if I may be permitted, through your pages, to state that I 

 have since satisfied myself that this was an error ; and that, similarly 

 to the Brick -earths of Grays and of the Lea valley, it belongs to the 

 lower or fluviatile terrace of the Thames gravel formation (x 5' of 

 my papers). 



I have seen no reason to qualify any of the other opinions expressed 

 by me in reference to the beds of the Thames, East Essex, and Can- 

 terbury heights gravel series. 



Searles V. Wood, Junr. 



Brent-wood, October 10, 1868. 



[1 We strongly recommend the perusal of Professor Huxley's Lecture " On the Animals which 

 are intermediate between Birds and Reptiles" as hearing on this subject. See Geol. Mag. 

 August, 1868, p. 357.— Edit. Geol. Mag.] 



