34 THE FOSSIL ECHINOIDEA 



arcs and in simple series, and the ornamentation is very simple. Possibly it may be a 

 young specimen of the species just described. 



The breadth is -j^ inch, and the height is not quite -^g inch. 



Illustrations of the Species in Plate VII. 



Fig. 8. The test : natural size. 



9. A poriferous zone and adjoining areas: magnified. 



There are two fragments of a test of a Cyphosoma from the locality which yielded 

 the more perfect specimens. One is part of a large form of the species just described ; 

 and the other belonged to a large test of another species. This test is characterized by 

 the elaborate ornamentation which exists between the vertically placed tubercles, whose 

 scrobicular circles are distinct. The intervening space is ornamented with small 

 tubercles, with mamelons and indefinite scrobicular circles of miliaries, and with some 

 large and small miliaries, which are irregularly placed. 



Genus ACANTHECHINUS, gen. nov. 



A large fragment of a regular Echinid allied to the Diadematidse, without apical 

 and aetinal portions, and showing one half of the rest of the test, is in the collection 

 from the Eanikot series. The details of the structures of the test are unlike those 

 of any known genus. The description of the specimen can only relate to the general 

 shape and the details of the ambulacral and interradial areas. 



We propose to include this form as a new genus ; for although it has some of 

 the characters of Stirechinus, Desor*, there are generic distinctions to be observed 

 between them. 



Test turban-shaped. Ambulacra convex from side to side, one half the breadth 

 of the interradial areas, with two incomplete vertical rows of primaries. Pores in 

 numerous pairs, forming a double series near the apex only. Interradials with sunken 

 median areas, plates distinctly sutured and high. Primary tubercles of both areas well 

 developed, some on raised areolae, all with a broad-based tumid boss and a small mamelon ; 

 they are imperforate, but largely creuulate, with ridges passing down their flanks. 

 Secondaries or large miliaries sharply pointed and spiny. 



The species may be called Acanthechinus nodulosus. 



1. Acanthechinus nodulosus. Plate VIII, Figs. 1-3. 



The original shape of the test was probably turban-shaped, or depressed and 

 circular, or subpentagonal in marginal contour. It was flat actinally, bulged at the 

 ambitus and for a short distance above, and it sloped gradually upwards to the apex, 

 being less convex there. 



Compared with the interradials, the ambulacral areas are small, but nearly as 

 prominent. At the ambitus the width of the ambulacrum is not more than that of one 



* Desor, 'Synopsis des Echinides Fossiles,' p. 131. Stirechinus SeillcB, Desor, =^cAi?itts Scillce, Desm., 

 from the Pliocene of Palermo and Monte Mario. 



