40 Reviews — Fauna of the Spiti Shales. 



to the strictly systematic portion in which two new genera and many 

 new species are described there is a short and vivid description of 

 the geography of Triassic North America, and a table giving the 

 interregional correlation of the Triassic areas. The work is copiously 

 illustrated with ninety-nine quarto plates. 



V. — Fauna of the Spiti Shales. 



THE report upon the fauna of the Spiti Shales is continued in 

 Palceontologia Indica by pt. ii of vol. iv (4to, pp. 397-456, 

 pis. xciv-c), in which Dr. Karl Holdhaus contributes a study (translated 

 by Mr. E. W. Vredenburg) of the Lamellibranchia and Gastropoda. 



Dr. Holdhaus describes a new and interesting genus, Cosmomya, 

 the precise systematic position of which is doubtful, and about 

 twenty new species of Lamellibranchia. The Gastropoda from the 

 Shales are poorly represented, a new species of Pleurotomaria, 

 a poorly preserved Cerithium, and the cast of an indeterminable form 

 being the only material available for study. Careful and exhaustive 

 descriptions of the new species are given, and Dr. Holdhaus enters 

 a plea for full and correct descriptions in palasontological literature. 



As the author points out, the Lamellibranchia do not possess the 

 same importance from the stratigraphical point of view as other 

 groups of animals, and in this case they do nothing more than 

 endorse the conclusions based on a study of the Ammonites. A few 

 forms point to Upper Jurassic age for the Shales, but on the 

 whole the Lamellibranchia supply no precise indications of age. 

 Dr. Holdhaus treats the faunistic relations of the group with caution. 

 He restricts himself to inferring a possible connexion with the 

 Jurassic faunas of Europe, but points out the occurrence of forms 

 which may indicate other affinities, for instance with Somaliland and 

 Arabia. He also ventures to suggest a close connexion with the 

 Jurassic of Kachh, though he admits that the Lamellibranch fauna 

 of the latter is as yet imperfectly known. On the whole, the Spiti 

 Shales Lamellibranchia appear to be eminently specialized, and, with 

 due qualifications, Dr. Holdhaus states that he is unable to point to 

 a single species (with the exception of some species of Astarte with 

 possible Kachh relationships) as truly identical with the fossils of 

 other Jurassic regions. 



VI. — Ceinoids and Dolomite. By E. W. Clarke and 

 W. C. Wheeler. 



MESSRS. F. W. CLARKE and W. C. Wheeler (United States 

 Geological Survey, Professional Paper 90-D ; June 16, 1914) 

 have followed up observations made by H. "W". Nichols (1906) 

 and A. H. Clark (1911), and have analysed the skeletons of 

 specimens belonging to nineteen genera of recent crinoids. As in the 

 previous cases, all contained magnesium carbonate in proportions 

 varying from 7-28 to 12-69 per cent. The available data show 

 a general increase of this constituent with increase of temperature in 

 the water, but the reason for this relation is not clear. The skeletons 



