MILLIPEDS OF FAMILY LYSIOPETALIDAE — LOOMIS 105 



The first member of the Lysiopetalidae discovered in North Amer- 

 ica was described by Say in 1821 under the name Julus lactarius. 

 Brandt, in 1840, recognized the generic distinctness of this species 

 from the European members of the family and placed it in a new 

 genus, Spirostrephon. Many subsequent writers have treated this 

 genus as a synonym of Lysiopetalum or of GaUipus^ although the 

 error of so doing was pointed out in 1895.^ 



Until quite recent years no additions have been made to the family 

 in this country since the description of lactar^lum in 1821, although 

 in 1880 Karsch described two species of Lysiopetalum^ supposed to 

 have come from North America, but they probably came from some 

 part of the Old World instead. In comparison with lactarium^ these 

 species were described as cylindrical, instead of depressed, with the 

 lateral crests not stronger than the dorsal ones. In all the American 

 species the pore-bearing carinae and two other large crests on each 

 side of the body are more prominent than the dorsal crests. In 

 Karsch's Lysiopetalwn setigeinim the segments are said to be clothed 

 ("vestitis") with hairs, while in L. costatum the dorsal carinae are 

 not interrupted along the front of the first segment, except that a 

 small median area is nearly smooth. 



In the present study of this family the published generic and 

 specific descriptions of Spirostrephon lactaHum were found to be 

 too inadequate in details for satisfactory comparisons to be made 

 with other North American members of the family, so that it appears 

 necessary to include supplementary descriptions. 



Genus SPIROSTREPHON Brandt 



Body small, slender, subcylindric, slightly depressed, 25 to 40 mm 

 long, 15 to 17 times longer than broad. Males less flattened than the 

 females and slightly more attenuate in front. 



Eyes forming a triangular cluster of 50 to 60 ocelli in 10 or 11 

 rows, counting from the top of the head; the adjacent sense organ 

 about as large as an ocellus. 



Antennae with joint 2 longer than any other, though not much 

 exceeding joints 3 and 5, which are equal in length, and joint 4, which 

 is nearly as long; joint 6 about two-thirds as long as joint 5 and about 

 three times as long as joint 7. 



First segment semicircular, with 20 longitudinal crests of uniform 

 height along the posterior margin of the segment ; the median crests 

 about two-thirds as long as the segment, the submedian crests shorter 

 than the middle or lateral crests; across the segment there are 10 

 setae arranged in a subtriarcuate series extending forward and in- 



iCook, O. F.. Amer. Nat., vol. 29. pp. 1017-1019. 1895. 

 92193—37 2 



