26 The Craspedosomatid^ of North America. 



pugnatorial pores as a means of defense. There is no reason for 

 supposing that the members of this family have or ever had any 

 thing like repugnatoral pores, notwithstanding such statements 

 as "Annuli with two pores on each side of the median line. — 

 Pseudotremia,"* and the characterization found in some of 

 the more careful European works " Repugnatorial pores obso- 

 lete," or " repugnatorial pores evanescent." In the one case the 

 the sockets of the lateral setae have been taken for pores, while in 

 the other there has been an unwillingness to sa}^ " pores want- 

 ing," on account of their constant presence in other families. 



The six setigerous tubercles of each segment are perhaps the 

 most distinctive family character. In some species the setae or 

 tubercles or both are microscopic and rudimentar}^, but this only 

 shows the tenacity of the character, as in no other recent family 

 are there similar bristles. 



In common with the Lysiopetalidse the pedigerous laminae are 

 all distinct from the otherwise complete segmental rings. 



It seems to us that the combination of these last three charac- 

 ters, want of repugnatorial pores, six setae or spines, and the free 

 pedal laminae is sufficient ground for the opinion that the Cras- 

 pedosomatidae have of all living Diplopoda the greatest resem- 

 blance to the carboniferous group Archipol^^poda. 



That the relationship is very close we do not contend, but 

 merely that the similarities are greater than in other recent forms 

 and are not merely apparent but real. 



The spines of existing Chordeumidae are insignificant in size 

 when compared with those of some of the fossil genera, such as 

 Acantherpestes, but ai-e the same in number, arrangement and 

 method of attachment to the segments, i. e., they stand in socket- 

 like bases. Moreover there were other carboniferous forms 

 which had bristles proportionall}' not much, if an}^, larger than 

 those of Trichopetalum and Scoterpes, and of the same shape. 



Other minor characters reinforce the above view, such as the 

 large size of the head, prominent e3'es, fusiform, somewhat flat- 

 tened body and long legs. 



That Chordeumidae were probably more abundant in former 

 geologic periods is seen from the fact that a considerable number 



* Dr. Cope informed me recently that this statement was the result of acci- 

 dent by which the words " Spirostrephon " and " Pseudotremia " were substi- 

 tuted for each other. [O. F. C] 



