MILLIPEDS — HOFFMAN 183 



or none at all. I have been fortunate, in this respect, in being able to 

 study the types of five of the ten names based upon species of Pachy- 

 desmus. These are: 



Fontaria clara Chamberlin 1918, in MCZ 

 Pachydesmus retrorsus Chamberlin 1921, in MCZ 

 Pachydesmus duplex Chamberlin 1939, in RVC 

 Pachydesmus simulans Chamberlin 1942, in RVC 

 Pachydesmus denticiilatus Chamberlin 1946, in RVC 



Material undoubtedly conspecific with the types has been seen 

 of all of the remaining names except Fontaria louisiana Chamberlin, 

 the status of which is still uncertain. The holotype of Fontaria 

 laticollis Attems was in the Berlin Museum and not readily available, 

 but in this case, as also with Pachydesmus incursus and P. kisatchinsis 

 Chamberlin, specimens are at hand which match the original de- 

 scriptions in every respect. Two very old specimens from Mississippi 

 in the U. S. National Museum may possibly be part of the type series 

 of Polydesmus crassicutis Wood. 



The illustrations in this paper were made with the use of a binocu- 

 lar microscope fitted with an ocular reticule, with great care being 

 taken to orient the structures into approximately the same position 

 before the drawings were made. Copulatory structures were removed 

 in all cases, and adherent membrane and muscle tissue dissected away. 

 Measurements of total length of specimens were made as uniformly 

 as possible, care being taken to avoid undue stretching or compressing 

 of the animals. Such measurements are probably accurate to about 

 a millimeter or two of being the correct length. 



Acknowledgments 



For the loan of, or access to, much of the material studied, I am 

 indebted to Henry S. Dybas and R. L. Wenzel and Drs. W. J. Gertsch, 

 J. F. G. Clarke, P. J. Darlington, and N. B. Causey. Dr. Ralph V. 

 Chamberlin is due a special note of thanks for his generous loan of 

 type specimens without which this work could not have been com- 

 pleted. For the material in my collection, I am deeply grateful to 

 Dr. Ralph E. Crabill, Jr., to Dr. Robert W. Lichtw^rdt, and particu- 

 larly to my good friend Leslie Hubricht, who, during his field work in 

 connection with terrestrial moUusks, has obtained more pachydesmids 

 than all other collectors combined. 



Review of the Literature 



The first species of Pachydesmus to be described was named in 1864 

 by H. C, Wood. His description of Polydesmus crassicutis, although 

 brief, was quite accurate, and the woodcut illustration of the male 

 gonopod published a year later in the "Myriapoda of North America" 

 is detailed enough to show the characters now considered to be diag- 



