28 ECHINODERMS OF THE LONDON CLAY. 



Genus — Spatangus, Klein. 

 (See page 13.) 



1. Spatangus Omalii. Plate III, fig. 9. 



Spatangus Omalii, Galeotti, Mem. sur le Const. Geol. de la Province de Brabant, 

 p. 191, pi., supp., fig. 1. 



Mr. Edwards has found at Barton fragments of a true Spatangus. These, on 

 comparison with an authentic example of the Spatangus Omalii of Galeotti, brought by 

 Sir Charles Lyell from Eocene strata in Belgium, prove to be, almost beyond a doubt, 

 identical with that species. I have figured the fragments with a restoration founded on 

 the Belgian Spatangus. 



The body was rather broadly cordate, and depressed above. The fragments preserved 

 show that the elevation of the dorsal surface was moderately uniform, and that the margins 

 were rather compressed. The dorso-lateral petals were lanceolate, with truncate 

 extremities. They were placed quite at the surface of the test, and their pores were 

 connected by grooves. The surface of the plates appears as if punctated and minutely 

 granulated. Within the anterior and lateral interambulacral spaces, are a few scattered 

 large and deep areolae surrounding elevated bosses, bearing the primary tubercles. These 

 were absent from the hinder extremity of the test. The ventral surface was plane, or 

 slightly concave, and bore numerous large primary tubercles with thin areolae. The mouth 

 and vent are not preserved. 



The best preserved fragment indicates a length of six tenths of an inch, and a breadth 

 of rather less dimensions. 



Order.— ASTERIDEA. 



(See page 17.) 



Family. — Asteri^;. 



The star-fishes of this group have regularly depressed flattened bodies, their upper 

 surfaces covered with paxilla? or coronated spines, and their margins bordered by a regular 

 double series of plates. They have no anal pore. 



Genus — Astropecten, Linck, 



Body stellate, few (five) rayed ; rays flat on both sides, regular ; surface of the skin 

 dorsally, and upper surfaces of the rays covered with paxillse. No vent. Ambulacra 

 bordered by spines, and furnished with two rows of suckers. Margins of the rays bordered 

 by a double row of conspicuous plates. 



