162 S. II. Scudder— Diversity of Type in ancient Myriapods. 



been lost by fire. Messrs. Meek and Worthen have also exam- 

 ined a second specimen, so that five in all have now been 

 studied. Only one of these, that procured by Mr. Bliss, is 

 preserved in such a way as to show the legs, and, until its dis- 

 covery, the affinities of this animal would necessarily have 

 remained very obscure. 



But for my previous study of the Archipolypoda of Mazon 

 Creek, and the revelation which these ancient types give of the 

 divergence of structure between extinct and modern forms of 

 Myriapoda, it would have been difficult to reach the full con- 

 viction that Pal ocampa was a myriaj "1. It is a eaterpillar- 

 like, segmented creature, three or four centimeters long, com- 

 posed of ten similar and equal segments besides a small head; 

 each of the segments excepting the head bears a single pair of 

 stout, clumsy, subfusiform, bluntly pointed legs, as long as the 

 width of the body, aud apparently composed of several equal 

 joints. Each segment also bears four cylindrical but spreading 

 bunches of very densely packed, stiff, "slender, blufttly tipped, 

 rod-like spines, a little longer than the legs. The bunches are 

 seated on mammillae and arranged in dorsopleural and lateral 



The individual rods have an intricate structure ; instead of 

 being striate, as supposed by Meek and Worthen in their last 

 fcion, they are furnished externally with about eighteen 

 longitudii ia es, about half as high as their dis- 



tance apart ; the edges of these ridges are broken into slight 

 serrations at regular intervals about equal to the distance be- 

 tween neighboring ridges, the highest point of each serration 

 being toward the apex of the spine ; the body of the ridge 

 itself appears as if broken at each serration. The intervening 

 space between neighboring ridges is equally divided by two 

 or three exactly similar, but miniature ridges, serrated at more 

 frequent intervals. This serration of both larger and smaller 

 ridges, with the apparent jointing or incision of the ridges to 

 the base at the lowest point of each serration, gives the whole 

 spine a jointed appearance; but a close inspection of the floor 

 of the spine itself between the ridges shows no sign whatever 

 of any break in its perfectly smooth surface. The diameter of 

 the spines is only about one-tenth of a millimeter, and yet it 

 gives room for an exquisitely regular division of its peripherv 

 by seventy or more delicate ridges, every fourth one higher 

 than the intervening, and all broken at minute intervals by 

 uniform serrations. The preservation of these structures from 

 Carboniferous times is only less remarkable than the occur- 

 rence, apparently so near the origin of the type to which it be- 

 longs, of ornamentation of such excessive delicacy, finish, 

 complication and regularity. 1 cannot discover that dermal 



