Prof. T. G. Bonnet/ — Effect of Pressure on Serpentine. 533 



Taking a review of the fossil Isopoda, we may venture to arrange 

 them provisionally as follows : — 



I. BopyridjE. Popyrus, sp. (parasitic under carapace of Palwocorystts), 



Upper Greensand, Cambridge. 

 II. iEGiniE. Palaga, 4 species, 2 Cretaceous, 2 Tertiary. 



JEgiles, 1 species, Oolite, Solenhofen. 

 Archceoniscus, 2 species, Purbeck, Swanage, etc. 

 III. Arcturid;e. Praarcturus, 1 species, Old Red, Hereford. 



Arlhrophura, 1 species, Coal Measures. 

 IV. Sph^eromidje. SpJucroma, 4 species, Tertiary, Italy, Calabria, etc. 

 Eosphmroma, 2 species, Eocene, Isle of Wight. 

 Eospharoma (=Palceoniscus), 2 species, Eocene and Miocene. 

 Arclmosphwroma, 1 species, Miocene, Bohemia. 

 Cyclosphccroma, 1 species, Great Oolite, Northampton. 

 Cymodocea, 1 species, Tertiary. 

 V. Oniscid^e. Oniscus, 1 species, Tertiary (in amber). 



Triconiscus, 1 species, Tertiary (in amber). 

 Porcellio, 3 species, Tertiary (in amber). 

 Armadillo, 1 species, Miocene, Oeningen. 



EXPLANATION OF PLATE XV. 



Figs. l-«, b, c. Cyctosphceroma trilobatum, H. Woodw., sp. nov., Great Oolite, 

 Northampton. 



Fig. la. Specimen natural size (a position of flagellum of antenna). 



Fig. lb. The same as fig. a, enlarged li times. 



Fig. \c. The same, front view of cephalon, a antennule ; a, part of the antenna ; 

 e epistomial plate. 



Figs. 2a, b, c. Cerutoceplialus Grayanus (A. White, MS.) living; Bass's Straits 

 (Mus. Brit, collection), about 4 times natural size. 



Fig. la. dorsal aspect. 



Fig. lb. ventral aspect. 



Fig. 2c. frontal aspect of head. 



Fig. 3. Spheeroma serratum, Fabr. sp. (length of living specimen about half an 

 inch). English and French coasts, found under stones. 



Fig. 4. ArcJmoniscus Brodiei, Milne-Edwards, Purbeck, Swanage, Dorset (mag- 

 nified 3 times), now referred to the JEgidce. 



II. — Note on the Effect of Pressure upon Serpentine in the 

 Pennine Alps. 



By Prof. T. G. Bonney, D.Sc, LL.D., F.R.S., F.G.S. 



IN some parts of the Alps serpentine is by no means a rare rock ; 

 indeed it is commoner than some geologists (myself included) 

 once supposed, because much that was formerly comprehended 

 under the term ' serpentinous schist ' now proves to be true 

 serpentine modified by the effects of pressure. 



An Alpine serpentine, when in its most normal condition, so far 

 as I have seen — and my experience is a fairly wide one — varies 

 usually in colour from a dark green to almost black, a red tint being 

 rare. Sometimes it is veined with a lighter green, and the rock that 

 has been affected by pressure is usually of a paler colour, ranging 

 from a fairly rich sage-green to a light greyish-green, the change 

 being no doubt, in part at least, the result of weathering. Small 

 grains of magnetite or chromite may often be detected. Except lor 

 this, the structure — apart from the results of mechanical action— is 

 usually compact, though varieties with glittering crystals of bronzite 

 and allied minerals occur. In this case the rock presents a con- 



