FROM THE GREAT OOLITE. 245 



The beautiful specimen, on a slab of Great Oolite from Yardley (fig. 2/), was collected 

 by Mr. Griesbach, and presented to me for this work ; it shows the spines in situ. The 

 primary spines are long, slender, and smooth ; in length, once and two thirds the diameter 

 of the test ; they have a small, conical head, with a prominent milled ring (fig. 2 e) ; the 

 stem tapers gently to the point, a transverse section shows it is somewhat triangular, with 

 flattened or rounded angles ; the surface, although apparently smooth, is covered with 

 microscopic longitudinal lines. The secondary spines are small, stout, dagger-like bodies 

 (fig. 2 g), with a flattened stem, and covered with longitudinal lines (fig. 2*). 



Affinities and differences. — This species closely resembles Acrosalenia Wiltonii, but is 

 distinguished by the following characters : it has larger equatoi ial tubercles, with more 

 prominent bosses and wider areolas ; the three superior tubercles more suddenly diminish 

 in size ; the miliary zone, even in the large granulated varieties, is narrower, the mouth is 

 larger, the notches are wider and deeper, the test is more depressed, and the sides less 

 inflated ; but the most marked character resides in the mouth opening which is small, 

 being about two fifths the diameter in Acrosalenia Wiltonii, and nearly one half the 

 diameter in Acrosalenia pustulata. 



Locality and Stratigraphical position. — This species has been collected by the Rev. 

 A. W. Griesbach, from the Eorest Marble at Oundle ; the Great Oolite at Yardley ; and 

 Wollaston; and also from Strixton, Wimmington, Blisworth, and Kingsthorp, Northampton- 

 shire. It was collected from the Great Oolite, near Woodstock, by Mr. Gavey ; and from 

 near Kiddington, Oxon, by Mr. Dominicke Brown, who kindly sent me a fine slab, with 

 fourteen urchins on its surface, which he obtained from a Great Oolite quarry. In 

 describing this specimen, Mr. Brown observes ■. " On examining the quarry where the 

 Cidaris {Acrosalenia pustulata) is found, I can see at once the reason why the shells are 

 not in a better state of preservation. The Cidarites appear only in a thin layer of rock 

 not more than a foot or two below the surface, then comes a thick bed of marl, and below 

 this the solid rock in which I occasionally find spines of Cidaris, but not often." This 

 species has been found by Mr. Bravender, in the Great Oolite and Bradford Clay near 

 Cirencester, and I have collected two specimens from the Forest Marble near Naunton 

 Downs, which are both depressed and highly granulated varieties ; I have seen separate 

 portions of the test on slabs of the Forest Marble near Upper Cubberley, Gloucestershire, 

 and in the Bradford Clay near the Tetbury-road Station, Great Western Railway, but I 

 have never seen even a fragment of a specimen in the Great Oolite, of Minchinhampton. 



