Reviews. 



Fossil Medusa. By C. D. Walcott. Monog. U. S. Geol. Sur- 

 vey, Vol. XXX, pp. 1-20 1, Plates I-XLVII, Washington, 

 1898. 



This monograph of the fossil medusas of the world, is the outcome 

 of a careful study of some 9000 specimens of these organisms from the 

 Middle Cambrian shales of the Coosa valley, Alabama. It was the 

 author's first intention to include his observations upon these fossils in 

 a work upon the Middle Cambrian fauna, but as the fossil medusas from 

 other geologic horizons and from other parts of the world became 

 involved in the investigation, the present monograph was prepared. 



Notwithstanding the evanescent character of these jelly-like organ- 

 isms, their fossil remains have been preserved in the Lower Cambrian 

 strata of New York and several European localities, in the Middle 

 Cambrian of Alabama, in the Permian of Saxony, and the Jurassic of 

 Bavaria. The Alabama specimens occur as more or less radiately 

 lobed, semi-cherty nodules which weather out from the shales in great 

 numbers. 



A new family, Brooksellidce, is founded for the reception of the gen- 

 era Brooksella and Laotira from Alabama and Dactyloidites, previously 

 described from the Lower Cambrian of New York. Two species of Brook- 

 sella and one of Laotira are described, and the one species of Dactyloid- 

 ites is redescribed, and it is surprising that the details of structure of 

 these ancient "jelly-fish" can be so fully determined. The generic 

 term Medusina is used for the designation of all those fossil Medusas 

 whose true generic relations cannot be fully determined, and in this 

 group are placed the three Cambrian species from Sweden. Some 

 observations are made upon the genus Eophyton in which have been 

 placed various trails which may have been produced by the tentacles of 

 floating medusas dragging upon the mud of the sea bottom, or by float- 

 ing seaweeds. The remaining pages of the volume are devoted to the 

 descriptions of the European Permian and Jurassic forms. 



Stuart Weller. 



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