60 THE FOSSIL ECHINOIDEA 



Memarks. The worn specimens of the larger types give a fallacious idea of the 

 poriferous zones ; for when well preserved they are traversed by a succession of bars 

 between the pairs of pores, and they are covered with a row of miliaries. The linear 

 nature of the pores is then shown and their conjugate nature. 



The petals never reach the margin ; and their inequality is very slight, and never 

 amounts to that of the typical Echinolampidse described by MM. d'Archiac and 

 Haime. The miliary median space inferiorly and the shape and position of the peri- 

 proct are worthy of notice. 



Premature Forms. The examination of the young forms gives some very interesting 

 results. 



The shape of the young forms is higher, more tumid, convex at the top, elongate ; 

 and the periproct is large and obliquely placed on the posterior margin, and invading 

 the under surface also. It is longitudinal and oval. The peristome is large and sub- 

 central. 



The poriferous zones in the very small forms are not developed near the ocular 

 pores, but they are further out. They are sensibly unequal, short, and the whole rosette 

 is anterior and small. The deficiency of pores in the anterior ambulacrum is remarkable 

 in some specimens. 



The next group, in point of size, show increasing elongation of the test, and the 

 unequal condition of the poriferous zone is palpaj3le. All this is seen in specimens ^ 

 inch in length, and in others in a less degree up to f inch. The test is then flatter, 

 but the large periproct and peristome are rather close together, the former transgressing 

 on the lower surface. The unequal pore-zones are not so definite. In some there is a 

 slight diff'erence in the size of the poriferous zones in the same petal. 



Illustrations of the Species in Plate XIV. 

 Eig. 4. The actinal aspect : natural size. 



5. Portion of the median granular band and periproct : magnified. 



6. Outline of the longitudinal profile of the test. 



7. Abactinal view of another specimen. 



8. Apical disk and portion of abactinal surface of another specimen : magnified. 



9. Abactinal aspect of a young specimen : natural size. 



10. Actinal aspect of the same: natural size. 



11. Abactinal aspect of a young specimen : natural size. 



12. Apical disk of the same specimen: magnified. 



13. Longitudinal outline of the same specimen : natural size. 



14. Actinal aspect of very young specimen : natural size. 



15. Longitudinal aspect of the same. 



16. Abactinal view of the same test : natural size. 



17. Peristome of a specimen one inch in length : magnified, 



18. Apical disk and surrounding structure of the same specimen (Fig. 14) : 



magnified. 



