the sixth endite of all the feet considerably 

 slenderer and longer in proportion than in A. 

 salina. The ovisacs were of the same propor- 

 tion but slenderer, and the head is slighter and 

 smaller in our American species " (p. 333). 



Different conclusions on neighboring pages, 

 in regard to the specific identity of closel}' allied 

 forms, might be accounted for in a careless 

 author ; but differences like these in statements 

 of observation betray inexplicable careless- 

 ness. 



In the chapter on geological succession, a 

 table of the geological and geographical distri- 

 bution of the known fossil species is given, and 

 also a diagram indicating the geological his- 

 tory of the orders of Crustacea, the sub-orders 

 of Branchiopoda, and the families of Phyllo- 

 poda. It is said that this diagram " ma}- also 

 serve as a genealogical tree, showing the prob- 

 able origin of the main divisions of the Crus- 

 tacea :" but the genealogical part of thediagram 

 consists simply of dotted lines connecting the 

 points of first appearance in geological histor}^ 

 of the Branchipodidae, Apodidae, and Clado- 

 cera, with the point of appearance of the Lira- 

 nadiidae in the Silurian ; the common stem 

 from this point with the Ostracoda in the upper 

 Laureutian ; and the branchiopod stem thus 

 formed, and continued to a hypothetical Pro- 

 tonauplius in the lower Laiirentian, with the 

 points of appearance of the Malacostraca, 

 Phyllocarida, and Cirripedia. On what con-* 

 ceivable theory of evolution this would repre- 

 sent a possible, much less the probable, origin 

 of the main divisions of the Crustacea, it is 

 hard to imagine, and was probably not serious- 

 ly considered by the author himself; for it is 

 far less like a probable genealogical tree than 

 the diagram on p. 448, illustrating the rela- 

 tions of the Phyllocarida to other Crustacea. 



In the chapter on morpholog}' and anatomy, 

 Professor Packard discusses at length the mor- 

 phology of the regions of the body and the 

 appendages of Arthropoda in general, and of 

 the crustacean limb in particular, and gives 

 some account of the anatomy of the phyllo- 

 pods, but adds very little to our previous 

 knowledge of the anatomy of the group. The 

 morphological discussion is an interesting con- 

 tribution to the subject, and, with the numerous 

 figures with which it is illustrated, will prove 



