Scudder.] 



66 



[May 24, 



Mr. Scudder also exhibited specimens of the curious myriapod 

 Polyxenus fascicularia Say, found with the preceding, and called 

 attention to the structure and disposition of the tegumentary 

 appendages. 



In a memoir just printed by the Society, 1 it is stated that modern 

 diplopod myriapoda are never supplied with any more striking dermal 

 appendages than serrate laminae, roughened tubercles or simple papilla- 

 mounted hairs. At that time Polyxenus was unknown to me in nature, 

 and I had not chanced to meet with special reference to its clothing. 

 In this striking exception to the above statement there are two classes of 

 dermal appendages. 



The first are those attached to the sides of the body-segments and border 

 the incisures on the upper surface. The simplest border the incisures and 

 are stout, more or less club-shaped spines (fig. 6, a.), often largest at the distal 

 extremity, lying with their bases next the incisures, those behind the inci- 

 .c sure being of uniform length and directed backward, those in 



front of it of variable length, generally alternating between short 

 and long, and directed forward ; they are all furnished with two 

 or more longitudinal rows of flattened teeth, directed apically 

 and outward. Toward the sides of the segments these spines 

 o-enerally assume the form of those belonging to the whorls on 

 b. the lateral mammillae, where the appendages present a uniform- 

 ily spreading hemisphere of points and consist of curved sabre- 

 shaped spines (fig. 6, b.), deeply and sharply serrate on the- 

 convex edge and increasingly so toward the pointed tip ; a 

 few much less conspicuous serrations often appear on the con- 

 cave side toward the tip. These spines are two or three times 

 longer than the club-shaped spines of the upper surface, but 

 Fig. 6. not much longer than those of the head, which approach them 

 also in structure, like those which arc found near the sides of the dorsal 

 surface of the body. 



But besides these two kinds, which show more or less tendency to blend, 

 there is another entirely distinct form, found only massed in a pair of dense 

 cylindrical fascicles, which occupy the whole of the posterior portion of the 

 dorsal surface of the terminal segment, and in life are directed straight 

 backward. These give the minute myriapod a very close resemblance to the 

 larva of Anthrenus, with which it agrees also in size. The individual spines 

 (fig. 6, c.) are shaped like a very elongated fish-hook, being exceedingly 

 slender, the shaft gently curved and the tip recurved and apically barbed ; 



i Archipolypoda, a subordinate type of spined myriapods from the Carboniferous 

 formation. Mem. Bost. Soc. Nat. Hist., m, 143-182, pi. 10-13. 



