LEPIDESTHES. 201 



about seven rows of subhexagonal plates, which appear to be of uniform size in all 

 the rows at the same level, and to be imbricated from below upwards. Inter- 

 ambulacral plates about 2 mm. in diameter, minutely granulated over their whole 

 surface, and ornamented by (1) an irregular circle of five small unequal tubercles 

 or warts, which have a minute perforated mamelon on a sloping elevated boss, and 

 are bordered by a minute linear furrow or areola, and (2) several much smaller 

 warts of various sizes. Spines very numerous (or crowded), acicular, sometimes 

 5 mm. long, covered with microscopic longitudinal grooves, and slightly expanded 

 at the base, which seems to be concave with a slight median projection. Ambu- 

 lacral areas with numerous (probably about seven) rows of rather smaller and 

 narrower plates (apparently of a rather wide curvilinear polygonal shape), each of 

 which bears close-set twin ambulacra, and which generally 'seem smooth, though 

 small tubercles are observable upon a few of them. Lantern-apparatus composed 

 of very large, smooth, wedge-shaped bones, some of which are 12 or 15 mm. long. 



Size. A flattened distorted specimen is about 120 mm. long and 55 mm. 

 wide. 



Localities. A large flattened example (on two slabs split horizontally) from 

 " the Pilton Beds, North Devon," is in the Museum of Practical Geology, and 

 another (almost entirely hidden by the matrix), from Ooyde, is in my Collec- 

 tion. 



Remarks. The best of these specimens appears to be an almost complete 

 test, but, having been flattened and then split through the centre, the plates 

 have become so confused that it is almost impossible to decipher it accurately, 

 though most of its characters may be said to be nearly clear. Occa- 

 sionally the hexagonal form of an interambulacral plate is evident; and their 

 imbricating character is undoubted, though it is not so easy to be sure of the 

 direction of the imbrication. These interambulacral plates do not all seem 

 tuberculated, but all are granulated. Their tubercles are clear and vary in size, but 

 they are always small : though irregularly placed, a roughly circular arrangement 

 of the five largest may often be traced. In one part seven plates at least may be 

 counted across the area. The ambulacral plates, again, are obscure in shape, but 

 they appear sometimes rather broader than high, and irregularly polygonal or 

 pentagonal, with some concave sides. They do not, as a rule, show any ornament 

 or granulation, but in one or two cases spiniferous tubercles can be seen upon 

 them. They evidently imbricate, and the imbrication seems probably to be in the 

 opposite direction to that of the interambulacral plates. The ambulacra are 

 large and very distinct, and perhaps are obliquely arranged, but this is not 

 certain. Judging from the casts of the ambulacra, the test must have been thin. 

 The spines, though always very small, seem to vary in length and thickness. 



From the present dimensions of our crushed specimens we may conclude that 



