CLASSIFICATION 529 



The classification here adopted is a compromise between ;i 

 natural system, so far as \ve can detect it, and an artificial 

 one. 



Two forms, separated from -one another by many differences, 

 show a minimum of degeneration, namely Decolopoda on the one 

 hand, and the Nymphonidae on the other. The former genus 

 lias live pairs of legs, and this peculiarity is shared by Pent>/- 

 II//I/I jilion. In both groups the three anterior limbs are all 

 present and well formed, save only that the ovigerous legs, whieh 

 have ten joints in Decolopoda, are reduced to five joints in the 

 Nymphons, and their denticulate spines, of which several ro\\s 

 are present in the former, are reduced to one row in the latter; 

 on the other hand, a greater or a less degeneration of these limits 

 marks each and all of the other families. 



Decolopoda is very probably the most primitive form knov\n. 

 1 hough it has characters which seem to be the reverse of 

 primitive in the dwarfish size of its chelophores and the crowded 

 eoaleseent segmentation of the trunk. Colossend.eis, in spite >f 

 its vanished chelophores, is probably closely allied: the shape 

 and segmentation of the body ;md the several rows of smooth 

 denticles on the ovigerous legs are points in common. The 

 Kuryeydidae. are closely allied to Colossendeidae ; they agree 

 with ])fi-nl<>i>i>il<i. in the two-jointed scape of the chelophore, and 

 with Ammotheidae in the dellexed mobile proboscis. The true 

 position of Jllii/in-li.nt.liin-ii.'' is very doubtful. 



The Nymphonidae and 1'allenidae are closely allied, and the 

 Phoxichilidiidae have points of resemblance, especially \\iih the 

 latter. A////'/>/M*// compare;- with Dimlti/iutlx in the completeni 

 of its parts, and is more typical in its long well-segmented body 

 and in its highly-developed chelae; hut it- already shows reduc- 

 tion in the scape of the ehelophore, in the pa.Ips. and in the 

 armature of the ovigerous legs. 



The I'hoxichilidae and I'yeiiogonidae I . \gnat lion ia. Leach | 



\chelata, Sarsj, though difld-ing greatly in aspect, are IHI! im- 

 probably allied to one another; and \\ hot her this be BO or nol . t he 

 complete absence of ehelnplmres and of palps a Holds an arbitrary 

 character by which they are conveniently separated from all the 

 rest. 



The following lahle epitomises the chid' characters <>f the 

 several families : 



VOL. IV 1' M 



