248 ACROSALENIA. 



ACROSALENIA HEMICIDAROIDES, JUNIOR? Wright. PI. XVI, fig. 4 a, 6. 



The small urchin, with spines attached, which forms the subject of fig. 4 a, b, was 

 collected by Mr. William Buy, from the same bed of clay, between the Forest Marble 

 and Cornbrash, from whence Acrosalenia hemicidaroides (PL XV, fig. 4^ was obtained. 

 At first, this specimen was thought to be distinct from that species, in consequence of the 

 spines being more cylindrical ; but as the test agrees with undeniable tests of A. hemi- 

 cidaroides, about the same size, I am disposed to consider the difference in the form of the 

 spines as depending on age. It may, however, hereafter be found to be a distinct species, 

 although in the mean time, until better evidence is obtained, I regard it as the young of 

 A. hemicidaroides, the materials at my disposal not enabling me to draw up a diagnosis. 

 Fig. 4 a shows the upper surface of the test, with the primary spines in situ, the longest of 

 which is once and two thirds the length of the diameter of the test ; the head and milled 

 ring agree in form with the same parts of the spine in A. hemicidaroides ; the stem swells 

 out a little in the middle, and tapers gently to the point ; the sides are slightly flattened 

 (fig. 4 b), and the surface is covered with fine, longitudinal lines : the secondary spines 

 are short, stout, dagger-like bodies, on the surface of which the longitudinal lines are more 

 distinctly marked, and the milled ring is proportionally more prominent than in the 

 primaries. 



Locality and Stratigraphical position. — From the band of clay between the Forest 

 Marble and Cornbrash, near Malmesbury, where it was associated with A. hemicidaroides 

 and numerous stems and fragments of Pentacrinus. 



Acrosalenia radiata, Forbes, nov. sp. 



" A. ambulacris angustis, tuberculis parvis seriebus, duobus approximatis alternatis sub- 

 divergentibus dispositis; inter-ambulacrorum tuberculis numerosis regulariter graduatis, 

 superne decrescentibus centro-lateralibus mediocribus, areolis disjunctis ; area centrali 

 angusta pauci granulata, granulis sparsis. 



" Diameter, seven twelfths of an inch ; altitude, three tenths of an inch. 



" It has affinities with A. spinosa, but differs in having the primary tubercles regularly 

 diminishing instead of suddenly decreasing above." (Mus. Pract. Geol.) 



Locality. — Collected by Mr. Lycett in the Great Oolite of Minchinhampton. 



