^36 



BULLETIN 63^ UNITED STATES NATIONAL MUSEUM. 



To the first class belong those forms which have had origin from 

 the primitive escJischoUsii, {/racilis, and acutkauda rami. 



The accompanying genealogical diagram will elucidate my meaning. 



The more recent derivatives of the eschscholtzii ramus are our pres- 

 ent eschseholtzii^ lucce^ and tennipes-wickhami ; of the gracilis ramus, 

 our present gracilis^ distans, and suhcylindrica ( ? ) ; of the acuti- 

 cauda ramus, the present acuticauda, and laticollis. Around each of 

 these more recent forms are the present incipient species and i-aces 

 which render our species so polymorphous. 



Armata 

 Impolens 



S"ul)eyi 



AcuticaiKia 



I 



Tenvripes 



ickhanti 



LaticoUis/ {H ^\feiitricosa 



Ancestral! Trunk 



Fig. 5. GENEALO(iI0AL IJIAGRAM OF THE DeNTII'ES GkOUP, SECTION B, SUBGENUS ElEODES. 



The recent derivatives of armata^ are militaAa and femornta by 

 the modification of general form and slow atrophy of the femoral 

 teeth; there are edentate forms derived from these species at the 

 present time in Lower California, and two of them are before me. 



An example of this loss of the femoral teeth is our impoteTis. I 

 have studied very instructive series of armata from Fresno and 

 Merced counties. These series show all intermediate stages between 

 a typical armata and a typical dentipes. 



These remarks are sufficient to indicate my ideas on this subject. 



Distribution. — The species of Section B are found inhabiting six 

 States or regions: Mexico, Texas, New Mexico, Arizona, California, 

 and Lower California. 



