242 Scientific Intelligence. 



and Cj'clostomata. Of new genera there are 37, but since 1917 

 these authors have described elsewhere 64 additional ones. This 

 certainly is a tremendous stride forward in our knowledege of 

 these organisms. 



In the oldest Eocene Aquia formation, there are 22 and all are 

 restricted forms ; in the Midwayian series 66, and only 3 of these 

 go higher; in the Claibornian there are 30, of which 20 go 

 upward; but in the Jacksonian there are 431, with 48 passing 

 upward, 17 coming in from the Claibornian below, and 2 from the 

 Midwayian; in the Vicksburgian there are 193, and of these 48 

 are from the Jacksonian, 6 from the Claibornian, and 1 from the 

 Midwayian. These figures show that bryozoans in general are 

 chronologically not long ranging, and that only about 16 per 

 cent pass through more than one series. On the other hand, the 

 work also shows forcibly that these animals have a wide range 

 geographically, inany of them being common to Europe and 

 America, and even to Asia, Australia, and South America. For 

 these reasons, bryozoans, when present, are fine index fossils, and 

 at many localities they are the only reliable time markers for 

 the strata. 



The junior author has been the stimulator of this great under- 

 taking, and he has been instrumental in getting together the 

 material through his own efforts and those of others, separating 

 the species, making the thousands of photographs, and seeing the 

 memoir through the press. The senior author, with his wide 

 knowledge of living Bryozoa, was thus enabled to bring to life, 

 as it were, these fossil forms, and to classify the great mass of 

 material unearthed in America. We see here a fine combination 

 of matured knowledge with the activity of a collector who knew 

 that great results lay ahead. And truly great results are here 

 attained, not only in classification and phylogeny, but even far 

 more in the morphology of calcareous bryozoan structures. The 

 work teems with morphologic drawings, and the plates illustrate 

 the species as one sees them under the microscope by means of 

 photographs that are but slightly retouched. c. s. 



20. A Monograph of the Naiades of Pennsylvania. Part III, 

 Systematic Account of the Genera and Species; by Arnold E. 

 Ortmann. Mem. Carnegie Mus., vol. 8, No. 1, 384 pp., 21 pis., 

 34 text figs., 1919. — In this large and handsome monograph are 

 described in great detail 80 forms of fresh-water pearl shells 

 found living in the rivers of Pennsylvania. They are arranged 

 under 32 group terms, and all are illustrated on plates. The 

 distribution is given in detail. It is a monumental work. 



c. s. 



