BRITISH FOSSILS. 



s 



Each avenue is composed of two series of ambulacral ossicles, 

 about sixty in a row, their inner edges being minutely crenulated 

 and accurately meeting along the centro-sutural line. These ossicles 

 are shaped something like a dice box,* each divided into two more 

 expanded portions and a central narrower part. The inner portion 

 is flattened or slightly excavated, and somewhat rhomboidal, the 

 outer elevated into a ridge. The middle and more contracted 

 portion is carinated obliquely, and on the inner (proximal) side 

 has a triangular groove. A similar groove occurs on the outer 

 (distal) side, placed nearer the middle than the former. The sides 

 of the ossicles are widely excavated for the purpose of forming the 

 ambulacral perforation through which the soft suckers or ambul- 

 acral feet passed. The interambulacral ossicles are rather quadrate, 

 and divided diagonally, though somevdiat irregularly and lobe-like, 

 into two portions, of which the inner or inferior portion is elevated, 

 and the outer depressed. These ossicles change shape, and become 

 narrower as they approach the buccal regions of the ventral disk. 

 Their crests or elevated portions bear combs of long slender acicular 

 spines, with bulbous bases ; of these spines there are from four to six 

 in each transverse row. The arrangement of the dorsal surface of 

 the arms is too obscure in the few portions of those organs that are 

 reversed to enable me to make out their details with certainty ; 

 but I think I can perceive pretty clearly the paxillated character 

 of the spines, and that these bodies, forming the radiated or brush- 

 like crowns of the paxillag above described, are much shorter and 

 stouter than the marginal spines. 



Locality and Geological Fosition. — In the Oolite of Wind- 

 rush Quarry, near Northleach, Gloucestershire. (Collection of Earl 

 Ducie.) 



* They are mucli less bent, even near tlie mouth, than in the recent S.papposus. — J.W.S. 



Descruption of the Plate. 



Fig. L Solaster Moretonis, natural size. 

 Fig. 2. Magnified ambulacral ossicles. 



Fig. 3. The same, with some interambulacral ossicles magnified, — the comb-like spices 

 attached. 



Fig. 4. Inner (proximal) portion of the ambulacrum, with its large angle-cf sicula, 



and their spines. 

 Fig. 5. Reticular pattern of the ossicles of the disk. 



E. FoHBES (1854). 



March 1856. 



