38 CIDARIS. 



rows, above and below ; these areas, therefore, are enlarged in the middle, and taper towards 

 the peristome and towards the apical disc, whereas in Cidaris Bouchardii they retain 

 very nearly a uniform width throughout. There are seldom more than four tubercular 

 plates in each column in Cidaris coronata ; whereas in Cidaris Bouchardii, although a 

 small species, the numbers are from six to seven. In Cidaris coronata the scrobicular 

 circles of the upper tubercular plates are separated by a considerable granulated space, 

 whereas in Cidaris Bouchardii the scrobicular circles are contiguous ; the granules of the 

 scrobicular circles are likewise larger and more spaced out in Cidaris coronata than in 

 Cidaris Bouchardii, and the primary tubercles are proportionately larger in the former. 

 Although both urchins have zigzag depressions down the centre of the inter-ambulacral 

 areas, in Cidaris coronata the miliary zone is much wider, and covered with larger granules. 

 The poriferous zones are sunk in very deep depressions in Cidaris coronata, arising from 

 the prominence of the granules on the ambulacral and inter-ambulacral areas, but these 

 zonal depressions are not so deep in our species. 



Cidaris Bouchardii resembles Cidaris propinqua, Minister, only in the depressed form 

 of the test. In all other points it is sufficiently distinct from that species. In Cidaris 

 propinqua there are four primary tubercles in each column of tubercular plates ; and those 

 on the upper surface are very large in proportion to the size of the test ; their areolas have 

 entire scrobicular circles of large spaced-out granules, which are closely contiguous ; the 

 ambulacral areas are much flexed, and have two rows of close-set marginal granules ; the 

 poriferous zones are slightly sunk, and have very small holes. The spines of Cidaris 

 propinqua have an elliptical-shaped body, covered with longitudinal rows of small tubercles, 

 and united together by connecting calcareous threads. 



Cidaris Bouchardii resembles Cidaris marginata, Goldf., in the depressed form of the 

 test, and in having, like it, deep sunk areolas, with a wide, depressed, much granulated 

 miliary zone, between the primary tubercles ; but it is distinguished from Cidaris margi- 

 nata in having narrower ambulacral areas, with only two rows of granules ; whilst Cidaris 

 marginata has four rows throughout. The primary tubercles are likewise smaller, and 

 their bosses are sharply crenulated ; whilst in Cidaris marginata they are smooth and 

 uncrenulated. This magnificent Coral Rag German urchin is, moreover, a much larger 

 form than our species from the Inferior Oolite. 



Locality and Stratigraphical position. — This is a very rare urchin, and was discovered 

 by us about three years ago in the Pea Grit of the Inferior Oolite of Birdlip and Crickley 

 Hills. Since PI. I was finished, we have obtained the finest specimen yet known, which 

 presents many points of importance that are not shown in our earlier found specimens. 

 This urchin is figured in PI. VIII, fig. 3 a, b, c. We collected, with Dr. Syme, Cidaris 

 Bouchardii in the Inferior Oolite near Bridport, Dorsetshire, in beds which are equivalent 

 to the Upper Ragstones of the Inferior Oolite of Gloucestershire. The Dorsetshire speci- 

 mens were associated with Collyrites ringens, Collyrites bicordatus, and Clypeus alius, being 



