438 Mr. S. H. Scudder on the 



spines on all the segments in longitudinal rows. An oppor- 

 tunity of examining a series of these animals from the same 

 locality, due to the kindness of Messrs. Carr and Worthen, 

 and especially of studying a fine fragment of Euphoberia 

 major ^ M. & W., giving an admirable view of the ventral 

 plates, proves that the differences between these ancient types 

 and modern forms are so numerous and important as to 

 compel us to refer them to a distinct suborder, for which the 

 name of Archipolypoda is proposed. 



One main distinction between the two groups, Diplopoda 

 (or Chilognatha) and Chilopoda, into which existing Myri- 

 opoda are generally divided, consists in the relation of the 

 ventral to the dorsal plates of the various segments of which 

 the body is composed. In the Chilopoda there is a single 

 ventral plate, bearing one pair of legs, for every dorsal plate ; 

 in the Diplopoda, on the contrary, there are two such ventral 

 plates, each bearing a pair of legs, for every dorsal plate 

 (with the exception of a few segments at the extremities of 

 the body). The Diplopoda are universally considered the 

 lower of the two in their organization ; and it is therefore not 

 surprising to find that no Chilopoda have been found in rocks 

 older than the Tertiary series * ; while Myriopods with two 

 pairs of legs corresponding to each dorsal plate may be found 

 as far back as the Coal-measures. In such comparisons as 

 are here instituted, the Chilopoda may therefore be left out 

 of account. 



In modern Diplopoda each segment of the body is almost 

 entirely composed of the dorsal plate, forming a nearly com- 

 plete ring ; for it encircles, as a general rule, nine tenths of the 

 body, leaving small room for the pair of ventral plates. On 

 the side of the body it is perforated by a minute foramen, the 

 opening of an odoriferous gland. Usually the ring is nearly 

 circular ; but occasionally the body is considerably flattened, 

 and the sides are somewhat expanded into flattened laminae 

 with a smooth or serrate margin ; a few species are provided 

 with minute hairs, sometimes perched on little papillae ; and 

 the surface of the body, ordinarily smooth or at best wrinkled, 

 is occasionally beset with roughened tubercles, which may 

 even form jagged projections. So far as I am aware, no 

 nearer approach to spines occurs on the dorsal plate than the 

 serrate edges of the lateral laminaj, the roughened tubercles, or 

 the papilla-mounted hairs. 



In the Euphoherice from the Coal-measures a very different 

 condition of things obtains. The segments of the body 



* Geophilus proavus, Germ., from tlie Jura, is certainly anereid worm, as 

 stated by Hagen. 



