Structure and Affinities of Euphoberia. 439 



may be circular, or laterally compressed, or, as in many modem 

 types, depressed ; but in all the dorsal plate occupies scarcely 

 more than two thirds of the circuit of the body, or even less, 

 being opposed by broad ventral plates. This dorsal plate is 

 not perforated for foramina repugnatoria*, but, as means of 

 defence, it is armed with two or three huge spines upon either 

 side : one row (for they occur on all the segments alike) lies 

 above, near the middle line of the body ; another is placed 

 low down upon the sides, near the lower margin of the dorsal 

 plate ; and a third row is sometimes found between them. 

 These spines are sometimes forked at the tip ; and they are 

 (probably) always provided to a greater or less extent with 

 spinules springing from the base or the stem ; sometimes 

 these are so numerous as to form a whorl of little spines 

 around the main stem. Usually the main spines are at least 

 half as long as the diameter of the body ; often they are as 

 long as the diameter ; and one may readily picture the different 

 appearance between one of these creatures, perhaps a foot or 

 more in length, bristling all over with a coarse tangle of 

 thorny spines, and the smooth galley-worm of the present 

 day. 



If we pass to the ventral plates we shall find differences of 

 even greater significance. In modern Diplopoda these plates 

 are minute ; the anterior forms the anterior edge of the seg- 

 ment, continuous with that of the dorsal plate ; together, how- 

 ever, they are not so long as the dorsal plate at their side ; and 

 the latter appears partly to encircle the posterior of the ventral 

 plates by extending inward towards the coxal cavities. The 

 legs are attached to the posterior edge of each ventral plate ; 

 and those of opposite sides are so closely crowded together 

 that they absolutely touch. The stigmata, of which there is 

 a pair to each ventral plate, are placed at the outer edge, 

 rather towards the front margin ; and their openings are longi- 

 tudinal {i. e. they lie athwart the segment) ; the coxaj of the 

 legs of the anterior plate are theretore opposite the stigmata 

 of the posterior plate. No other organs are found upon the 

 ventral plates ; one might indeed say there was not room for 

 them. The legs themselves are composed of six simple 

 cylindrical joints subequal in length, the apical armed with a 

 single terminal claw ; the whole leg is short, generally not 

 more than half as long as the diameter of the body. 



In the ancient Euphoherio' all is very different. The ventral 



* This is what would be expected from the presence of spines ; for two 

 such means of defence should not be looked for in the same animal ; ofi'eii- 

 sive glands are present only in slow-moving or otherwise defenceless 

 creatures, as in Phasmidse among Orthoptera for example. 



