GENEEA AND GEOUPS OF THE ECHIjSTOIDEA. 75 



G-enus Miceopedina, Cotteau, 1866, PaZ. Arcing., Terr. Gret. 

 vol. vii. p. 822, pi. 1197. fig. 8. StoUczTca, 1873, Cret. 

 Fauna of S. India, vol. iv. 3 ser. viii. 3. Ecliin. p. 41, 

 pi. vi. Be Lof-iol, 1887, Faime Cret. du Port., Ech. fasc. i. 

 p. 61, pi. X. 



Test of moderate size, circular in tumid ambital outline, sphe- 

 roidal, depressed actinally, or generally depressed. 



Apical system small. 



Ambulacra straight, slightly prominent ; pairs of pores flush, 

 in a narrow zone, either in straight or oblique series of triplets, 

 the adoral pair being remotest from the interradium, and the 

 aboral close to it. Plates low, composed of a low, broad, median 

 primary component, and of adoral and aboral demi-plates, or the 

 adoral may be a primary, the sutures convex towards the tubercles. 

 Interporiferous area with several vertical rows of very small 

 perforate, smooth, primary tubercles, most not reaching the apex. 



Interradia with numerous low, broad, coronal plates, with very 

 numerous vertical rows of primaries resembling those of the am- 

 bulacra, some of the plates with oblique rows. Earely more than 

 two vertical rows reach the apex. 



Peristome small, circular ; branchial incisions small. 



Fossil. Cretaceous : Europe, N. Africa, S. India, Asia. 



The next genus is represented by a very fine species in the 

 Inferior Oolite oi YrSLnce, Seterocidaris Trigeri, Cutteau, and by 

 a small fragment of a probably second species, H. wickense, 

 Wright, from the Inferior Oolite of Yorkshire. But althou"-h 



o 



Cotteau had the advantage of examining a fine specimen which 

 was admirably drawn by Humbert, Wright, under unfavourable 

 circumstances, placed the species in their proper family, and 

 noted the affinities with Astropyga of the recent fauna. Pollow- 

 ing Wright, I am able to confirm his judgment in some points, 

 after an examination of the structures of the ambulacra and 

 peristome. Cotteau placed the genus amongst the Cidaridte 

 and distinguished it from any of the Diademafcidse. This is 

 to be regretted because really so much of our knowledge about 

 the form is derived from his excellent work and Humbert's 

 masterly drawing. Wright missed the points which I would 

 press upon the distinguished French Echinodermatist, and con- 

 sidered that the narrowness of the ambulacra and width of the 



