42 CIDAUIS. 



CiDARis coNFLUENs, Forbes, MS. 



CiDABis CONFLUENS. Morris, Catalogue of British Fossils, 2d edition, p. 74. 



— - — Woodward, Memoirs of the Geological Survey, Decade V, Note on 



species of Cidaris. 



The specimen consists of four consecutive plates, of nearly equal size, from one of the 

 inter-ambulacral rows. The set measures one inch in length and half an inch in width. 

 The areolas are oblong and excavated, with acute lateral margins, but they are all confluent 

 above and below ; the bosses have broad, prominent, deeply crenulated summits ; the 

 tubercles are small, and widely perforated ; the lateral borders of the plates supported 

 small granulations. The spines imbedded in the same rock were long, cylindrical, and 

 longitudinally striated ; their surface was armed, at intervals, with short, stout, forward- 

 directed prickles. The ambulacra! areas are absent ; and the surface of the plates is so 

 much weathered, that I did not consider it necessary to figure the specimen. 



This fragment resembles very much Cidaris Lorierii, Wright, from the etage Bajocien, 

 or Inferior Oolite, of the department of the Sarthe (a description of which will be found in 

 the notes of foreign species of the genus Cidaris), but the weathered and fractured 

 condition of the fragment renders it impossible to make a more correct diagnosis until 

 better specimens are found. 



Locality and Stratigrapliical position. — The specimen belongs to the Museum of 

 Practical Geology, Jermyn Street ; and was obtained from the Inferior Oolite, near Frome, 

 Somersetshire. 



C. Species from the Bradford Clay. 



Cidaris Bradfordensis, Wright. PL V, fig. 7 a, b, c, d. 



Form and size unknown ; ambulacral areas narrow, with two rows of marginal 

 granules ; inter-ambulacral plates thick, areola circular, boss prominent, summit feebly 

 crenulated, tubercle large ; a complete scrobicular circle of fifteen large granules around 

 the areola ; miliary zone concave, with six to eight rows of granules ; the spines, associated 

 with the plates, have the acetabulum small, the neck long and smooth ; the stem elliptical, 

 and covered with waved lines of granules, neither uniform in size nor arrangement. 



Description. — The meagre materials at my disposal, illustrative of this urchin, only 

 permit me to give a very imperfect diagnosis of this Oolitic form, which I at one time 



