ECHINITES. 209 



sandstone of Silphoue moor, is unfortunately incomplete in the 

 margin. 



To another division of the same class belongs No. 13, wliich 

 appears to be conulus albogalerus; the same kind of fossil that is 

 figured in Plot's Oxfordshire, Tab. II. Fig. 13, and in Parkinson's 

 Org. Rem. III. PI. II. Fig. 10, 11. The specimen, which is from the 

 alluvium, is rather defaced ; and having something of a projecting 

 ridge at the narrower end, extending from the vei'tex to the base, it 

 perhaps ought rather to be considered as a cassis, or helmet-stone. 

 Like most other echinites, it has ten double rows of pores, or hiporous 

 ambulacra, as they are called ; with intervening spaces, alternately 

 broad and narrow. The conulus albogalerus occurs in the chalk and 

 the oolite, as Avell as in the alluvium. In the oolite and the chalk is 

 also found that species of cassis called echinocorys scutatus, figured in 

 Parkinson's Org. Rem. III. PI. II. Fig. 4. 



Fig. 6 represents a very interesting though imperfect specimen, 

 from the alluvium at Whitby, which is also of the catocysti class. It 

 is distinguished by this peculiarity, that instead of avenues of pores, 

 it has avenues of minute short spines. These spines are so dis- 

 posed as to form a flower with five petals, as in No. 5 ; and as in that, 

 the petals are depressed ; but with this difterence, that whereas the 

 middle part of each petal in No. 5 is elevated, and only the margin 

 depressed, the whole of each petal in No. 6 is depressed, and the 

 middle more than the margin. The vertex or centre of the flower is also 

 sunk, and has five spines around it, opposite the five spaces between 

 the petals. The petals, properly so called, do not occupy the whole 

 breadth of the disk, but terminate about half way between the vertex 

 and the margin. Each petal contains two double rows of minute 

 spines, diverging from the edge of the central or vertical hole ; and at 

 the termination of the petal, the double rows converge, and become 

 single rows ; so that, instead of four rows, only two proceed from 



3 F 



