1871.] 331 [Wilder. 



crimination of species within the same genus; although Owen once 

 held a different opinion. (Trans. Zool. Soc, vol. n., p. 379, 1838). 



But how can we reconcile the above generalization with the state- 

 ment of Dr. J. E. Gray, 1 that with the Balaenidse and Balsenopteri- 

 dse, " every bone of each genus is peculiar, though not always easy to 

 describe; likewise, almost every bone of each species, especially the 

 ribs and phalanges, the skull, tympanic bones, scapula> and cervical 

 vertebrae" ? Is it not probable that there are not only specific but in- 

 dividual differences between two individuals in each and every part 

 of the body, and in each and every possible attribute of these parts; 

 but that these differences are more obvious in some/ parts than in 

 others, so that certain parts and attributes are more available than 

 others? and such a view is by no means incompatible with the result 

 of our experience, and with the analysis of other matters which lead 

 us to believe that for the determination of more important and com- 

 prehensive questions, we must look to the central and essential parts, 

 while minor questions may be decided by observation of peripheral 

 and less vital organs. For instance, a single vertebra would enable 

 us to say whether its owner were a reptile, a bird, or a mammal; but 

 it would far less distinctly exhibit the particular genus or species to 

 which it belonged; on the other hand, the manus of the whales and 

 of the Sirenia resemble each other, and even that of the penguin 

 might not be at once recognizable as that of a different class ; but 

 within the same order or family, the genus would be at once appa- 

 rent from the special proportions of the parts. 



According to Gray, 2 the long spine which has been described as 

 Myriosteon Higginsii, was thought by some to be the tail of a ray, but 

 is probably part of a starfish ; certain pointed fossils are thought by 

 Pander to be teeth of selachians, by Owen to be from the borders 

 of the suckers of cuttlefish; the " ichyodorulites " have been regarded 

 as spines of Crustacea by some authors, but as selachian spines 

 by Agassiz 3 ; from which the latter concludes that these parts are at 

 any rate not available as either branch, class, ordinal, or perhaps 

 family characters, but rather as generic ; the " bird-tracks " in the 

 Red Sandstone of the Connecticut Valley, did not at once indicate 

 whether the feet which made them belonged to birds or to reptiles; 



iProc. Zool. Soc, 1864, p. 228. 

 sproc. Zool. Soc, 1864, p. 163. 

 3 Lectures on Selachians, Dec. 1867; (unpublished). 



