364 



s. GOTO : 



cellaria to each plate and it may be situated anywhere close to 

 the naked space, the more usual position being near the centre 

 of the plate. 



Mouth-plates. — The relative size of the mouth-plates is different 

 in different specimens, being as long as 8 mm. in one with E= 

 335 mm. and only 5 mm. in another of R=:338 mm. On the 

 furrow margin of each plate there is a series of very stout, flat- 

 tened spines, 12-15 in number. Tliose near the mouth end are 

 usually slightly larger than the others, but not very conspicuous- 

 ly so, so that the spines are more nearly equal to one another (PI. 

 X, fig. 158). On the actinal surface of each plate there are some 

 half a dozen or more spines, either forming a single row along 

 the suture hue of the plate or more irregularly arranged ; one of 

 them at the mouth end is usually conspicuously larger than the 

 others, which are usually short and even granuliform. Each 

 mouth-plate is seen to present towards the ambulacral furrow a 

 keeled surface similar to those of the adambulacral plates. 



Ventrolaterals. — The ventrolaterals are very numerous. There 

 is a longitudinal row of plates larger than the others immediate- 

 ly outside the adambulacrals running out two-thirds or more into 

 the arms, and bearing more and larger pedicellariae than the 

 other plates. One can also distinguish a second series running 

 out about half way or slightly more into the arms ; a third series 

 may sometimes be made out with difficulty, but the plates are 

 much more irregularly arranged. The ventrolateral plates are, 

 generally speaking, larger towards the ambulacral furrow and the 

 mouth, so that the plates near the intcrbracliial margin are smaller 

 than the others. The ventrolateral plates are uniformly covered 

 with granules and are closely set. Many of them bear pedicel- 



