Prof. E. Forbes on a new genus of Cretaceous Echinidte. 443 



raent of the plates of the genital disk as in Ananchytes and 

 Holaster. Anus supramarginal. A fasciole proceeding from 

 beneath it, and making a circuit without sinuosities around 

 the margin of the body, including the dorsal ambulacra just 

 above it. Mouth transverse, inferior, anterior, lodged in the 

 termination of the anteal furrow, its upper lip tumid, but not 

 projecting over it. Dorsal and ventral surface with numerous 

 secondary tubercles surrounded by miliary granules, a few larger 

 or primary tubercles on the antero-lateral areas or cheeks. Spines 

 unknown. 



The following reputed species of Spatangus and Holaster be- 

 long to this genus : — 



1. " Spatangu^" excentricus, Woodward, loc.cit. 



Chalk of Kent and chalk-flints in Norfolk. Specimens of this 

 very rare and strangely-shaped species, which undergoes most 

 extraordinary changes of form in its course from youth to age, 

 are contained in the collections of Mr. Bowerbank and Mr. Wethe- 

 rell, and in the Museum of Practical Geology. It was discovered 

 by Mr. Rose of Swaffham. 



2. " Spatangus " cordiformis, Woodward, loc. cit. 



Specimens from the chalk of Norfolk are contained in the 

 Museum of Practical Geology. 



3. " Holaster" cequalis, Portlock, Report on Londonderry, &c. 

 pi. 17. fig. 3. 



Chalk of the north of Ireland. An examination of the original 

 specimens has convinced me that this is identical with C. cordi- 

 formis. The original of the figure pi. 17. fig. 1 in the same 

 work, referred to the Holaster Sandoz of Agassiz, appears to be 

 a bad specimen of a tumid variety of the C. cordiformis ; but of 

 this I am not quite sure. 



4. " Ananchytes cinctus" and 



5. " Ananchytes fimbriatus," 



both figured and briefly described by Morton in his ' Cata- 

 logue of the Cretaceous Fossils of New Jersey,' are also members 

 of this genus. Whether distinct from the British species and 

 from each other remains to be seen. 



6. " Holaster Greenoughii," Agassiz, Cat. Raisonne, Annales des 



Sc. Nat. tom. viii. p. 27. 



Of this we have no figure or description, only the following 

 notice : — " Espece renflee, tres voisine de VH. cinctus ; mais le 



