Geolofjical 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 e{)iphyses 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 tiie 

 excessively numerous minute jjlates which form ttie interambulacrH. 

 Reference is made to Echinocj/stis pointon, Wyv. Thomson ; and to 

 a species of Protocidaris, Whidborne, from Low^er 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. AVoodward founded the genus Eudadia. The Author 

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

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

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

 plates were exposed which it was possible to certainly identify 

 with vertebra] 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 Eudadia, and are provisionally referred to that genus. 

 The number of arras 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 Eudadin, is founded on a small, well-preserved 

 specimen from the Wenlock Limestone of Crolt Farm. In this 

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

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

 soni as many as seven are present. Eudadia 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 Euryala?. They are defintd 

 Rs Ojjhiurida possessing paired series of arms, covered externally 

 by imbricating [dates, but devoid of ambulacral ossicles. The bucci.l 

 armature is abnormal. 



2. ' Note 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.ll.S. 



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

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

 Tissiugton cutting. They present themselves as sections througii 

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

 and the form cannot be referred with certainty to any recognized 

 order of Sponges. The spicules were doubtless originally siliceous, 



