INDUSTRIAL PROGRESS DURING THE YEAR 1876. clvii 



Excellent plates accompany the article, which is written in the En- 

 glish language. 



The embryology of the mollusks has been studied by Fol, Ray- 

 Lankester, Rabl, Jhering, and Bobretzky ; while Professor Leydig has 

 23ublished, in Troschel's Archiv, an elaborate account of the shells 

 and tegumentary coverings of the gastropod mollusks. Rabl's paper 

 on the development of Uiiio^ in the Jenaisclie Zeitschrift^ is especially 

 noteworthy. 



An interesting article on the habits of the singular fluviatile shell 

 lo is contributed to the American Naturalist by Dr. Lewis. They 

 live in the rivers of Tennessee, and are so solid and of such bright 

 colors that they might be mistaken for sea-shells. It seems that they 

 were known to the Indians before the advent of European races, as 

 they have been found in their graves. 



The last annual report of Professor Hayden's United States Geo- 

 logical Survey contains an excellent account of the snails collected 

 in Colorado by Mr. E. Ingersoll. Six new species were collected, and 

 much interesting information given regarding the vertical distribu- 

 tion of the species found. 



Besides Rabl's later paper, a very fully illustrated memoir on the 

 development of the fresh-water mussels {Unio and Anodontd) of Eu- 

 rope, by W. Flemming, had been previously published in the Pro- 

 ceedings of the Royal Academy of Science of Vienna for 1875. The 

 papers will interest American students, since these mussels so abound 

 in our rivers. Similar but less extended researches have been carried 

 on in this country by Dr. W. K. Brooks, but we believe they are as yet 

 unpublished. 



The great work of Mr. F. B. Meek on the " Invertebrate Cretaceous 

 and Tertiary Fossils of the Upper Missouri " is illustrated by forty- 

 five plates, and treats principally of fossil mollusks. It will be indis- 

 I^ensable to the geologist of the far "West, as the different divisions 

 of the cretaceous and tertiary ages were originally established by 

 the invertebrate remains therein described, and it therefore forms the 

 basis of our knowledge of the two most important formations in the 

 West. 



A large volume on the fauna of the land and fresh-water shells 

 of Northeastern Africa, by Carl F. Jickeli, has recently appeared. A 

 number of forms, reaching as far south as Zanzibar, are included. 

 The work is accompanied by eleven excellent plates. Though bear- 

 ing date 1874, it has only recently been received in this country. 



Dr. W. K. Brooks, in a paper entitled " Afiinity of the MoUusca 

 and MoUuscoida " (polyzoa and brachiopods), suggests that the tuni- 

 cates are not mollusks, and that the polyzoa and brachiopods are 

 derived from the worms. He also, as others have suggested, thinks 

 that the mollusks are also derived from the worms. He believes 

 that the polyzoa originated from a type like the brachiopods. Thus 



