ECHTNODERMATA. 45 



of small granules ; mouth opening small, peristome pentagonal ; apical disc opening large 

 and pentagonal ; primary spines with large, thick, cylindrical stems, ornamented with 

 longitudinal rows of prominent, forward- directed granules ; secondary spines short and 

 spatulate, covered with fine longitudinal lines ; tertiary spines small, conical, or oval shaped. 



Dimensions. — a. Large specimen : Equatorial diameter, two inches and four tenths of 



an inch ; height, one inch and seven twentieths of 



an inch. 

 B, Large specimen : Equatorial diameter, two inches and two tenths of 



an inch \ height, one inch and four tenths of an 



inch. 

 c. Usual-sized specimen : Equatorial diameter, one inch and four tenths 



of an inch ; height, one inch and four tenths of 



an inch. 



Description. — This noble urchin was very abundant in the Corallian Seas of Europe, 

 and its test and spines form characteristic fossils of this stage of the Jurassic group. Much 

 confusion regarding this species has been caused by Goldfuss having figured, along with 

 the test of Cidaris Blumenhachii, Miinster, the spines of three or four other species of urchins, 

 and especially in having erroneously described the spines of Cidaris florigemma as 

 belonging to the test of Cidaris Blumenbachii. I am indebted to my friend 

 Mr. S. P. Woodward for having called my attention to this subject, as he has always 

 maintained that Cidaris florigemma, Phil., was distinct from Cidaris Blumenhaclni, Goldf. 

 Having been fortunate in finding the slab, figured in PL II, fig. 2 a, containing a small 

 Cidaris florigemma with spines attached, I had direct evidence that the spines figured by 

 Goldfuss as those of Cidaris BlumenhacMi in reality belonged to the Wiltshire urchin. 

 The next point to be ascertained was, whether the test figured by Goldfuss was different 

 from the test of this species. A critical examination and comparison of good type speci- 

 mens of Cidaris Blumenhachii, one -in the collection of the British Museum, and another 

 kindly sent me by Dr. Eraas, of Stuttgard, with the specimen figured in PI. II, fig. 2 /5, c, 

 has proved that they are very distinct from each other. 



Plott, in 1677, figured the spines of this urchin under the name of Lapides Judaici. 

 He says — " We find them here (Oxfordshire) of different sizes, from about two inches 

 in length and an inch and a half in circuit, downwards to an inch and less in length and 

 not much above half an inch round. Most of them have a pedicle from which they seem 

 to have had their growth, and are ridged and channelled the whole length of the stone, 

 the ridges being parted with small knots set in quincunx order. As to their texture, I 

 find it to be very curious, made up of lamellae or little thin plates, not unlike the stone 

 Selenites ; only these are opaque, and the whole bulk of the stone indeed much different. 

 The plates, as in the Selenites, seem to be made up of strings, which in most of them run 



