74 THE AMERICAN NATURALIST. [Vol. XXXVII. 



pectoral region of vertebrates contains an account of the bones, 

 nerves, and muscles of the breast, shoulder, and wings of birds. In 

 addition to the admirably clear descriptions of the anatomy of these 

 organs, this part is of special interest in that it contains a full dis- 

 cussion of the systematic relations of the orders and families of 

 birds as well as an account of the relations of birds to other verte- 

 brates. The diphyletic origin of the birds as represented by the 

 Ratitoe and Carinatre is regarded as an untenable assumption by 

 Furbringer, who argues for the racial unity of the whole group. 

 From this standpoint the Ratitae represent either a primitive stock 

 from which the Carinatas have sprung or, as Furbringer believes, a 

 degenerate assemblage derived from the Carinata, 1 . The author 

 further believes that birds have had their origin from none of the 

 known orders of reptiles, but from an ancient stock among the very 

 oldest reptiles and of which at present no remains are known, p. 



Spiders of the United States. 1 — As the title indicates, this book 

 was written to meet a popular need. The first part, which is given 

 up to a short introduction on structure, collecting, and habits, might 

 very well have been enlarged. The remainder of the book is taken 

 up by a systematic account of spiders. 



About two hundred of the common species of the eastern United 

 States are described. The descriptions are short, often very short. 

 The illustrations are excellent. Each species has one and often four 

 figures to show the characteristic parts and markings. The common 

 round web species that are found in similar places are described 

 together. The photographs of the webs are especially good, and 

 from them the whole process of web making can be followed. 



The value of the book would have been increased for amateurs by 

 reference to a few of the popular books on spiders, and for more 

 advanced readers by the authorities of the species. 



BOTANY. 



The Yucceae. 2 — At a time when systematic activity is preponde 

 atingly segregative and the tendency to publish species separate] 



mmon Spiders of the Un 

 |2 5 PP-, 5°' figs. 



