326 Reviews — Geology of Central Noncay. 



The digitigrade Proterotlierium was more monodactyle even than 

 the horse ; the differences with the ' Solipeda ' are, however, con- 

 siderable. 



Nesodon, among the Plantigrada, has fore-limbs presenting more 

 analogies with the Carnivora and certain Rodents (e.g. the squirrels) 

 than with the herbivorous Uugulates. The fore-limbs of Homalodon- 

 therium at first sight recall those of an enormous Carnivore, but 

 like those of Nesodon were endowed with less mobility. 



Posterior limbs. — The posterior limbs of Pyrotlierium are, like the 

 anterior, those of a Eectigrade ; having to fulfil the same functions 

 as the posterior limbs of the Proboscidia and the Amblypoda, these 

 organs have converged in the three distinct groups. Astrapotlieriiim 

 also was apparently a Eectigrade ; the body being less massive than 

 in the typical Rectigrada, the posterior limbs were endowed with 

 a certain degree of mobility. 



Like the Rectigrada, the Digitigrada touched the ground with 

 their ungual phalanges only ; the conformation of their astragalus, 

 however, shows that their posterior limbs possessed a great amount 

 of flexibility. Besides, their limbs were slenderer and more 

 elegant. 



In the Plantigrada, on the contrary, the rotation of the tibia on 

 the astragalus was rather limited ; their fore-limbs being adapted to 

 prehensile or fossorial functions, they required a certain amount of 

 immobility in their posterior limbs. 



III. — Det centrale Norges fjeldbygning. By K. 0. Bjorlykke. 

 8 and 595 pages and map. With a supplement : Notes on 

 Graptolites from Bratland in Gadsdal, Norway. By Charles 

 Lapworth. 16 pages and plate. Norges Geologiske Under- 

 sogelse. No. 39. Kristiania, 1905. ^ 



rpHE first part of this memoir of the Geological Survej^ of Norway 

 j_ deals with the district around the Mjiisen Lake. The formation 

 known as Sparagmite is in great force. It lies unconformably on 

 the Archaean, and consists of — 



1. At the top, light-coloured felspathic sandstone and conglomerate. 



2. A limestone, the Biri-kalk. 



8. A conglomerate, the Biri-conglomerate. 



4. A dark-coloured sparagmite (felspathic sandstone). 



Above the Sparagmite Formation there is a quartz-sandstone and 

 grey-greenish shales, shown by the author to be allied to the blue 

 quartzite of Valdres, and above this come the schists, etc., of the 

 Silurian. The author gives a full account of the Sparagmite 

 Formation, and in his second part traces it into Osterdal, the valley 

 through which the Christiania-Trondhjem railway runs. 



The third part of the memoir deals with Gudbrandsdal. The 

 author describes some small patches of rock which underlie the dark 



1 "On the Geology of Central Norge," by K. 0. Bjorlykke. A summary of 

 a larger (the above) -work, 2 and 27 pages and map, Kristiania, 1905. 



