ECHINODERMATA. 27 



specimen of this species, with some of its spines attached, has been discovered ; and one 

 was found in the Lias of Yorkshire ; but these are the only examples with which we are 

 acquainted. The specimen which forms the subject of our figure was discovered by 

 G. E. Gavey, Esq., C.E., whilst cutting through the shales of the middle Lias, to form the 

 Oxford, Worcester, and Wolverhampton Railway; the zone of Lias in which it was 

 found was that containing Ammonites maculatus, Young and Bird; it was associated 

 with three or four other remarkable species of Asteriada, Ophiuridae, and Crinoidce, in a 

 high state of preservation, and which will be figured and described in the future parts of this 

 Monograph. The conditions under which these Echinoderms were found are curious and 

 deserve notice. TJraster Gaveyi, Forbes, was found lying on the upper surface of a slab of 

 sandstone, twelve inches thick, at twenty-five feet below the surface, associated with frag- 

 ments of Extracri'Hus, Ammonites, and other fossils. All the specimens of Tropidaster 

 pectinatus, Eorbes, and Cidaris Edwardsii, Wright, were found imbedded in the under 

 surface of a thick slab of ironstone, at twenty feet below the surface. Almost all the 

 specimens show the under surface uppermost, and most of them had their spines attached 

 to the spinigerous tubercles. Cidaris Edwardsii^ when first discovered, was so entirely 

 covered with spines, that the inter-ambulacral plates were almost concealed. For further 

 details relating to this section, and the fossils found therein, the reader is referred to 

 Mr. Gavey's paper.* 



The specimen is crushed and flattened, and lies with its mouth and jaws uppermost. 

 At our request, Mr. Baily, in his beautiful drawing, has restored the urchin to its globular 

 form ; but it must be added, that all the parts of the test, and the details he has given of 

 its structure, are faithful copies of the original. The ambulacra! areas are provided with 

 two rows of small perforated tubercles on the margin of the areas, each plate thereof 

 developing alternately a smaller and a larger marginal tubercle (PI. I, fig. 1 b) ; amongst 

 these a row of small granules are scattered somewhat irregularly throughout the areas. 

 All these tubercles supported short, stout, blunt-pointed spines (fig. 1 d, e), the surface 

 of which is delicately sculptured with longitudinal lines : many of these spines are seen in 

 situ in the specimen, although many have been removed to expose the surface of the 

 test. The poriferous zones are wide, and follow the gentle flexures of the ambulacral 

 areas ; the pores are large and oblong, and the two pores forming a pair are separated 

 by very thin partition walls, a circumstance which forms a good diagnostic character 

 (PI. I, fig. 1 b) ; there are five pairs of pores opposite each of the large tubercular plates. 



The inter-ambulacral areas are four times the width of the ambulacral ; they are com- 

 posed of rather narrow tubercular plates, which support two rows of primary tubercles, set, 

 therefore, rather closely together, in a vertical direction, so that the areolas are all confluent 

 above and below (PI. I, fig. 1 b) ; the miliary zone is wide, and filled with six rows of 

 minute, close-set, perforated tubercles, each of which is raised on an elevation of the test ; 



* ' Quarterly Journal of the Geological Society,' vol. ix, p. 29, ■vrith sections of the Railway Cuttings. 



