FROM THE LOWER WHITE CHALK. 181 



the centre of the plate ; the ridges on the plates resemble numbers of prominent gra- 

 nulations projecting outwards, which impart a granulose aspect to the surface of the disc, 

 and is very well represented in PI. XLI, fig. 3, and PI. XLIII, fig. 1 e ; a process 

 of each plate extends into the inter-ambulacra, the ornamentation of which differs from 

 that in the middle of the plate ; the punctuated lines are widest and more flexed, and this 

 incrusting process appears to blend with the granidations on the test ; the sur-anal plate is 

 elevated, and forms the anterior border of the periprocte ; the ocular plates are heart- 

 shaped, and more prominent than the ovarials ; they are likewise covered with punctuated 

 flexuous ridges, but the lines are more tortuous, and the style of ornamentation is different 

 (PI. XLIII, fig. 1 e) from that on the ovarials. 



The spines are not preserved in any of the Dover specimens that have passed through 

 my hands. M. Cotteau, however, describes them as elongate or aciculate, cylindrical, or a 

 little compressed, provided with fine longitudinal sub-granular striae ; their greatest dia- 

 meter is near the neck of the spine, and they regularly diminish to the upper extremity, 

 which is pointed. The collarette is short or absent, the milled ring very prominent and 

 strongly striated, and the rim of the articular cavity crenulated. 



Affinities mid Differences. — Salenia granulosa, Forb., strongly resembles Hyposalenia 

 heliophora, Desor, from the Chalk of Maestricht ; it is distinguished from it, however, 

 according to M. Cotteau, by being smaller in size, and having its upper surface more 

 conical, its ambulacra furnished below the ambitus with smaller granules, and in possessing 

 fewer primary tubercles in the inter-ambulacra ; the apical disc is thinner and distinctly 

 circumscribed, the flexuous ridges on the ovarial and ocular plates are more irregular and 

 more granular, and the periprocte is situated to the right of the axis. 



Locality and Stratic/rapldcal Position. — This fine species is found in the hard gritty 

 whitish beds of the Lower Chalk at Dover, where it is associated with Cyphosoma simplex, 

 Forb., and numerous Polyzoa. All the specimens I have examined were obtained from 

 this one locality, where it is rather rare. 



M. Cotteau states that it is a common species in the Jltage Senonien of Vernonnct, 

 Giverny, Petit-Andely, Penterville (Eure), and the environs of Beauvais (Oise). 



History. — M. I'Abbe Sorignet first described in 1850 this Salenia in his interesting 

 memoir 'I'Oursins de I'Eure,' and identified it as the Hyposalenia lieliophora, Desor. In 

 the same year the late Professor Forbes, in Dixon's ' Geology of Sussex,' gave a figure of 

 this Urchin, which he referred to Salenia scutiyera, Gray ; subsequently, in the second 

 edition of Morris's ' Catalogue of British Fossils,' 1854, Forbes separated it from that species 

 under the MS. name S. granulosa. In 1856 M. Cotteau, in M. Desor's 'Synopsis des 

 fichinides fossiles,' named the specimens collected and identified as Hyposalenia helio- 

 phora by M. Sorignet, Salenia incrustata, Cott. ; he gave the following diagnosis of 

 this form : — " Small Urchins, well characterized by their very large apical disc, thin, and 

 little in relief, and incrusting in some manner the whole of the upper surface of the test. 

 The ovarial plates present a series of small points disposed like rays around many centres ; 



