MILLIPEDS OF ORDER COLOBOGNATHA — LOOMIS 365 



One of the chief differences recognized between the previously es- 

 tablished species of Brachycyhe has been the number of segmentSc 

 the eastern lecontel having less than 50 and the western rosea more 

 than 60. Two new members of this genus are herein described, one 

 from each side of the continent. The conformity of each new spe- 

 cies, in number of segments, with the species previously known in 

 its respective region, may signify descent from a common ancestor, 

 but the structural differences between the two eastern species, or 

 between the two western ones, are sufficiently numerous and extreme 

 to have required a very long time for their development. The com- 

 mon prehistoric home of the two branches of the genus is a matter 

 of doubt but may have been Mexico or Central America rather than 

 the United States, as extension from a single source in the United 

 States to both sides of the continent is more difficult to explain 

 than migration from a more southern source. 



The four species of this genus are separated in the following key : 



KEY TO THE SPECIES OF BRACHTCYBE 



1. Head completely hicMen beneath first segment, which has the 



lateral cariuae produced foi'ward and expanded inward, oc- 

 cupying almost the entire front margin ; surface of disk very 



faintly tuberculate petasata, new species 



Head exposed between the short, oblique, lateral carinae of first 

 segment, the disk of which is strongly tuberculate 2 



2. Body stout, 4 or 5 times as long as broad ; number of segments 



not exceeding 50 lecontel Wood 



Body slenderer, 7 to 12 times as long as broad and with 60 

 to 75 segments 3 



3. Body about 7 times as long as broad; first segment with 3 



transverse rows of tubercles and with lateral carinae 

 obliquely produced forward; posterior margin of mid-body 



segments continuous throughout rosea Murray 



Body 10 to 12 times as long as broad ; first segment with 2 

 transverse rows of tubercles and with lateral carinae scarcely 

 produced ; posterior margin of mid-body segments interrupted 

 at base of each lateral carina producta, new species 



BRACHYCYBE PETASATA, new species 



Many specimens were collected in the Cherokee National Forest, 

 Tenn., November 1, 1929, by Dr. O. F. Cook. The type (U.S.N.M. 

 milliped no, 1160) is a male. 



Diagnosis. — The enlarged first segment, which completely hides 

 the head from above, immediately distinguishes this species. 



Description. — Length of largest specimen 18 mm, width 3 mm; 

 number of segments 40 to 49. Anterior end of body suddenly broad- 

 ened from in front. 



Head hidden beneath first segment when viewed from above (fig. 

 32, d). 



