ECHINUS. 



4. Echinus Henslovii. Plate I, fig. 7. 



o 



Body a sub-depressed spheroid. Ambulacral areas to interambulacral, as 1 — 2. 

 Plates of both areas thickly covered by small depressed granules and tubercles, disposed in 

 an obscurely radiating arrangement around a somewhat larger central tubercle. The 

 smaller tubercles densely crowded along the sutural lines. Pairs of pores disposed in 

 oblique rows of three pair becoming less oblique, and almost falling into line near the 

 apical disk. Apical disk rather large in proportion to breadth : its plates, in the only 

 specimen I have seen, are wanting. The under side of this example is entirely concealed. 

 Breadth, T 7 T ths of an inch ; height, T 4 T ths of an inch. 



A single specimen, in the cabinet of Mr. Searles Wood. It is from the Red Crag of 

 Walton. 



It is very nearly related to the Echinus Martinsii, an unpublished species, from 

 Iceland, preserved in the Museum of the Jardin des Plantes. 



5. Echinus Charlesworthii. Plate I, fig. 6. 



Arbacia, species of, Searles Wood, MS. in Morris, Cat. Brit. Foss., p. 48. 



Body nearly globose, with slightly tumid segments and impressed avenues ; the 

 former, thickly studded by minute crowded, nearly equal tubercles. The pairs of pores 

 are arranged in moderately oblique rows of three in a series. Between each pore of a pair 

 the ridge is slightly elevated, and here and there, upon the avenues, are minute granules. 

 The ambulacral plates bear each from three to five minute, globular, primary tubercles, 

 elevated upon narrow bosses, and differing but slightly in their dimensions. Between 

 them are thickly scattered granules. The interambulacral plates are very broad in pro- 

 portion to their height, and bear from nine to twelve primary tubercles, of which three or 

 four on the avenue-side of each plate are slightly larger than the others, and ranged more 

 regularly in a slightly oblique row, giving a somewhat undulated aspect to the sides. The 

 apical disk, which is destroyed, appears to have been small in proportion to a rather large 

 mouth. The finest specimen measures T Vth of an inch in diameter by T Vth of an inch in 

 height. 



I know no existing sea-urchin which can be compared with this pretty species. It is 

 from the Coralline Crag of Ramsholt. 



"S 



Genus — Temnechinus, Forbes. 



Body more or less spherical ; ambulacral and interambulacral segments developed, 

 bearing on their plate, whose sutural margins are mostly excavated, tubercles of various 

 sizes ; vent centrical. Genital disk surrounding the anal space composed of five 



