Geological Society. 427 



have been an Echinid, the ambulacra possess just such characters as 

 theory anticipates : au inner arch of poriferous ambulacral plates, 

 homologous with those of a starfish, is closed externally by a 

 series of paired plates, which represent the ambulacral series of 

 an urchin. 



The undoubted Asteroid affinities of the urchin lead to an 

 attempt to find homologies for the elements of 'Aristotle's Lantern' : 

 the pyramids are regarded as equivalent to the first pair of adambu- 

 lacral plates, the epiphyses to the corresponding pair of ambulacral 

 plates of the Echinoid series, and the teeth are compared to the 

 Asteroid odontophore, which has acquired a persistent root. 



A new genus assigned to the Echinida is characterized by the 

 excessively numerous minute plates which form the interambulacra. 

 Reference is made to Echinocystis pomum, Wyv. Thomson; and to 

 a species of Protocidaris, Whidborne, from Lower Ludlow beds, 

 which seems to be identical with the type-species found in Devonian 

 rocks. 



The results are given of a re-examination of the unique specimen 

 on which Dr. H. Woodward founded the genus Eucladia. The Author 

 agrees with Dr. Woodward in regarding the exposed surface of this 

 fossil as ventral ; it bears the buccal armature and madrcporite, 

 and gives origin to the arms. On slicing two of the arms, no 

 plates were exposed which it was possible to certainly identify 

 with vertebral ossicles. Some hollow casts, from the Lower Ludlow 

 of Leintwardine, which have hitherto been regarded as too problem- 

 atical for determination, are shown to represent an organism closely 

 allied to Eucladia, and are provisionally referred to that genus. 

 The number of arms in this new species is less than in the original 

 (E. Johnsoni), and they are more nearly equal in size. A new genus, 

 closely allied to Eucladia, is founded on a small, well-preserved 

 specimen from the Wenlock Limestone of Croft Farm. In this 

 the pairs of arms of each paired series are only two in number, 

 while in the new species of Eucladia at least four, and in E. John- 

 soni as many as seven are present. Eucladia and the new genus 

 are regarded as aberrant Ophiurids, and are placed in a new order 

 as a group of the same value as the Euryalae. They are defined 

 as Ophiurida possessing paired series of arms, covered externally 

 by imbricating plates, but devoid of ambulacral ossicles. The buccal 

 armature is abnormal. 



2. ' Xote on the Occurrence of Sponge-spicules in the Carboni- 

 ferous Limestone of Derbyshire.' By Prof. W. J. Sollas, M.A., 

 LL.D., D.Sc, F.R.S. 



Remains of sponge-spicules are fairly abundant in a rock-slice 

 taken from a specimen obtained by Mr. H. H. Arnold-Bemrose from 

 Tissingtou cutting. They present themselves as sections through 

 long cylindrical rods, but the terminations are obscure and indefinite, 

 and the form cannot 1 e referred with certainty to any recognized 

 order of Sponges. The spicules were doubtless originally siliceous, 



