223 GEO. H. HORN, M. D. 



family the arrangement of the others is the next subject of discussion. 



Here it is usual to review the modifications of the various parts of the 



external skeleton, but as most of the exceptional cases have already 



been jziven and as it is far more convenient to amplify under the 



tribal headings, it seems unnecessary to repeat them here, reserving 



for the present such remarks as may be proper to explain the reasons 



for the rejection of the old systems of classification and to defend 



that here proposed. 



The family originally indicated by Latreille was more restricted 



than at present, and to Schicedte is due the suggestion of adding the 



Anisotomini which had been considered a distinct family by Erichsoo 



and Stephens. Lacordaire divides the geuera into three tribes in the 



following manner : 



Posterior coxse distant Leptoderides. 



Posterior coxse contiguous. 



Posterior trochanters prominent SiJphidea. 



Posterior trochanters placed in the axis of the thighs Anisotomidea. 



Duval follows several years after with nearly the same system, 

 separating the Clambites as a distinct tribe by the coxal plates. 



The separation of Leptodirus in a distinct tribe by the distant 

 posterior coxae is certainly a very great exaggeration, and the char- 

 acter must be assigned rather a secondary rank in view of the fact 

 that all the blind genera and Lyrosoraa are so constructed. It is true 

 that Pholeuon and Oryotus were unknown to the above authors or 

 they would probably have seen the relationship existing between the 

 three, as Schaufuss (Stettin Zeitsch. 18(31, p. 42-1:), did a few years 

 after, although he appears to have overlooked entirely their resem- 

 blance to the Cholevini. 



The value of the hind trochanters in separating the other twA) 

 tribes is entirely illusory, in fact the character as made use of does 

 not exist, and it seems to me remarkable that characters once suc- 

 gested and gaining currency will oft&n pass unquestioned, and be 

 repeated from author to author until they become so fixed in the 

 books that it is nearly impossible i,o free ourselves from them. With- 

 out desiring to cite numerous examples in proof of the assertion, the 

 attention of students is invited to the trochanters themselves. 



The next system of classification is that proposed by C. Gr. Thomson, 

 (Skand. Col.). Here appears the first serious innovation and the first 

 suggestions toward a rational arrangement. He recognizes fully the 

 value of the structure of the anterior coxal cavities as a means toward 

 that end, and it is to be regretted that the limited founa of his country 



