30 PROCEEDINGS OF THE NATIONAL MUSEUM vol.86 



vided. Wliether this difference and several less important and less 

 constant features justify the maintenance of the two families is 

 hardly to be determined from the American material, and for the 

 present the division may be recognized and used without prejudice 

 to simplify classification. 



Attems 2 has tentatively, and apparently mistakenly, transferred 

 several American genera of Cambalidae to the Cambalopsidae, al- 

 though in no instance does the original description give justification 

 for such a course ; in fact, the remarks pertaining to the mentum in 

 these genera usually leave no doubt as to its divided structure and 

 would prohibit removal to the Cambalopsidae. 



ORDINAL POSITION OF THE CAMBALIDAE AND CAMBALOPSIDAE 



Comparing the Cambalidae and Cambalopsidae with the tropical 

 orders of cylindrical millipeds that have closed segments, the Ano- 

 cheta and Diplocheta, we find an association with the latter in the 

 absence of legs on segment 4; the presence of two pairs of legs on 

 segment 5; and the structure of the mouth parts and gonopods. Also 

 the segments of these two families are like those of the Diplocheta 

 in being divided by a transverse constriction into anterior and pos- 

 terior subsegments, while in the Anocheta the segments are divided 

 into three belts by two transverse sutures, which often may be seeu 

 distinctly, although sometimes scarcely perceptible. The pleural 

 sutures of the Anocheta do not appear in the Cambalidae or Cam- 

 balopsidae, except that pleural elements may be indicated by oblique 

 ridges that cross the posterior subsegment from the pedigerous lamina 

 to the posterior margin. Hence the Cambalidae and Cambalopsidae 

 have been placed in the Diplocheta as a suborder, the Cambaloidea. 

 equivalent to the Spirostreptoidea, which is a very large tropical 

 group. 



CHARACTERS OF THE CAMBALOIDEA OF THE UNITED STATES 



As has been stated, the most significant difference between the 

 Cambalidae and the Cambalopsidae is whether the mentum is entire 

 or is transversely divided, but inasmuch as the genera of these two 

 families may not be separated readily by other contrasting features 

 it is proposed to examine some of the outstanding characters of the 

 American members of the suborder without regard to family 

 alignment. 



The structural characters of the Cambaloidea of the United States 

 are very diverse, and only a few of them are common to all the 



' Kukenthal's Handbuch der Zoologie, vol. 4, p. 207, 1926. 



