FROM THE WHITE CHALK. 307 



by an arch of small tubercles, three tiers or more in depth, whilst the lower surface 

 of the border is closely covered with small granules, among which a few small tubercles 

 scattered here and there are seen. 



The body-plates of the test are throughout covered with very fine close-set granules, 

 and amongst these several small tubercles are disposed, from six to nine on each plate ; at 

 fig. 1 /, eight plates from the sides of the test have been carefully drawn and enlarged 

 three diameters ; in order that this arrangement on their surface, which is clearly demon- 

 strable in good specimens, may be shewn, for on these only can the structure be 

 discerned. 



The plates on the margins of the anteal sulcus are thickly studded with large 

 primary tubercles (fig. 1 c, e), which are raised on bosses with crenulated summits, and 

 surmounted by perforated tubercles (fig. 1 <f). The areola? around the bosses are 

 encircled by granules ; tubercles similar to these in form and structure are seen on the 

 cheeks of the shell, and a few are extended along the sides and on the central plates of 

 the rounded base (fig. 1 b). 



Forbes described the fasciole as " distinctly marked, passing under the vent and 

 continued on each side, even over the cheeks." Some indications of this fasciolar track 

 were drawn by my artist, who noted his impression in fig. 1 h; but I have seen nothing 

 that I would call a fasciole, such as we observe in Hemiastcrs, Micrasters, &c, in any of 

 the forms that have come under my examination. 



Locality and Stratigraphical Position. — This remarkable Urchin, with which I know 

 nothing to compare, was first observed by my old friend Mr. C. B. Rose, of SwafTIiam, 

 and communicated by him to Mr. Samuel Woodward, in whose ' Geology of Norfolk ' it 

 was first figured from specimens collected from the Upper and Medial Chalk of Norfolk. 



JJini lies and Differences. — Infulaster excentricus, Rose, very much resembles Infulaster 

 Hagenowi, Borchards, collected from the White Chalk of Staffin, in the Island of 

 Wollin, Pomerania. A model in wax was communicated to Professor d'Orbigny by Herr 

 von Hagcnow, in 1851, without any other indication of publication. A comparison of 

 specimens would alone enable the observer to decide on the affinities and differences of 

 the German as compared with the Norfolk form ; seeing that one of the specimens given 

 me by Mr. Rose very much resembles Infulaster Hagenowi, Borchards. 



Iniulaster rostratus, Forbes. PI. LXX, figs. 2, a—f; 3 a. 



Diagnosis.- — Test much compressed on the sides ; anteal sulcus long, deep, and 

 narrow, its sides rising high into a beak ; dorsal surface curved and carinated ; posterior 

 border obliquely truncated, bent in upper third ; sub-anal fasciole, well defined, and 

 extended on the flanks. 



