408 Dr. Senry Woodward — Photography in Geology. . 



gradually increasing in size posteriorly, the margins forming a con- 

 tinuous curve, those arising from the terga between and including 

 the second and seventh directed obliquely backwards, their transverse 

 axes inclined at an obtuse angle to those of the terga to which they 

 are attached. Ninth segment annular, encircling the subcircular 

 tergum of the tenth, which forms the anal valve. 



In the above quoted paper describing Anthracosiro looodwardi, it 

 was suggested that this genus should be classified in the same section 

 as Eophrynus and Kreischeria. The discovery of the structure of 

 the carapace as seen in A. fritschii shows this view to be untenable, 

 and establishes the right of Anthracosiro to stand in a distinct family, 

 if family rank be assigned, as has been done, to the analogous 

 differences between Anthracomartus and Eophrynus. In the structure 

 of the carapace Anthracosiro is more like Anthracomartus than 

 Eophrynus, while in the structure of the opisthosoma it differs 

 markedly from both. 



The characters of the three groups may be tabulated as follows : — 



a. Tergal laminge of opisthosoma directed obliquely backwards, 



their transverse axes inclined at an obtuse angle to the 



transverse axes of the terga, which in the posterior half 



of the body are scarcely, if at all, recurved ; carapace vaulted, 



widely depressed in the middle line above ; eyes represented 



by a pair of widely separated tubercles situated a short 



distance above the lateral margin ... Anthracosironidas. 



h. Tergal laminae of opisthosoma, with their transverse axes in all 



cases in the same line, whether curved or straight, as the 



transverse axes of the terga ; terga in the posterior half of 



the body becoming gradually more and more recurved 



towards the anal extremity ; eyes, when visible, close to 



the middle line of the carapace. 



a'. Carapace flattish or evenly vaulted, not differentiated by deep 



grooves into definite elevated areas ... Anthracomartidas. 



h'. Carapace dorsally differentiated into a median lobate axial 



elevation and a lateral flat segmentally grooved area. 



EophrynidsB. 



For the characters of the genera referred to the Anthracomartidse 



and Eophrynidai, reference may be made to my paper entitled 



" Eophrynus and Allied Carboniferous Arachnida" in the Geologhoal 



Magazine for October and November of last year. 



VI. — Photography in Geology. 



By Henry Woodward, LL.D., F.E.S., F.G.S. 



(PLATE XX.) 



PHOTOGEAPHY has now become so invaluable an accessory 

 to every branch of science, that it is not surprising to find it has 

 proved indispensable alike to the geologist and the palasontologist. 

 One has but to turn back over the four decades of this Magazine 

 and compare the number and quality of the illustrations, in the 

 earlier with the later years, in order to realize the great advances 



