some Species re furred to it, 55 



adoral end of each interambulacrum " ein Halbtafelchen, 

 wodurch die paarigeii Interambulacralreihen, in welchen die 

 Asseln alternieren^ gsgen das Peristom beglichen werden/'' 

 It must not be inferred from this that there was any relic of 

 the primitive median single interambulacral ; the plate in 

 question is merely the adoral plate of either the a or h column 

 in process of resorption. Tliis, if reckoned in, gives 7 plates 

 to the column in which it lies. 



Doederlein, Kolesch, and Spandel agree with Qaenstedtia 

 describing the interambulacral plates as five-sided. It is only 

 the extreme adoral or adapical plates that may be four-sided 

 in consequence of resorption or incomplete growth respectively. 

 As regards the normal interambulacrals, Spandel is right in 

 describing the adoral margin as convex, the adapical as 

 concave ; but this is not always obvious, nor is the curve 

 very regular. 



Doederlein noticed that the adambulacral margin was 

 sharply bevelled underneath, *' schneidend " ; but it was left 

 for iSpandel to observe the denticles on the bevel (see his 

 pi. xiii. f. 4 h). This is confirmed by Brit. Mus. E 1121 

 (PI. I. fig. 6), which further shows that the regular denti- 

 culation seen in Spandel^s figure is characteristic of the 

 ambital interambulacrals. Nearer the peristome the bevel 

 forms a less acute angle and the denticulation is less regular. 

 This agrees with what may be observed in allied species; but 

 for a full discussion of these interesting structures I must 

 refer to my memoir on the Bakony fossils. The same 

 specimen shows that there are about four denticles to each 

 ambital interambulacral (as figured by Spandel), whence it 

 may be inferred that there were also about four ambulacrala 

 to the interambulacral. Kolesch, arguing from the external 

 view of the margin, likewise inferred that 3-4 ambulacrala 

 went to a small interambulacral, 5-6 to the largest ones. 

 The denticles are not quite at right angles to the adradial 

 margin, as might be inferred from Spandel^s figure, but slope 

 slightly adradially and adorally, and from this it follows that 

 the ambulacrals lay at a corresponding angle. 



In the ' Triassic Echinoderms of Bakony ' the structure 

 of the sutures between the interambulacral plates in this and 

 allied species is discussed at some length, and my inability to 

 follow Spandel's account is there explained. Here it will be 

 enough to give the conclusions based on an independent 

 examination of the British Museum specimens as iuterpreted^ 

 in the light of the Lepidocidaridse. 



