1852.] LYELL — BELGIAN TERTIARY FORMATIONS. 341 



inch. Above it is regularly convex, with the apex eccentric and 

 anteal. In front of the apex, the anteal ambulacral region is de- 

 clining and depressed, but forms a tumid curve before reaching the 

 margin. Behind it the back rises gradually and describes a regularly 

 swelling but rapidly declining curve, until it reaches the posterior 

 margin. The ambulacral petals of the back are lanceolate ; that of 

 the anteal ambulacrum is nearly symmetrical ; the lateral ones are 

 slightly inequilateral ; the posterolaterals are slightly longer than the 

 antero-laterals. They diverge at a considerable angle, and their 

 extremities do not approach the margin so nearly as those of the 

 antero-laterals. There are about fifty-two pairs of pores in each row 

 in the anteal ambulacrum, and seventy or more in the lateral. They 

 are placed in very slight depressions, and the pores are connected by 

 grooves, separated by narrow granulated ridges. The whole surface 

 of the test above and below is studded with nearly equal minute tu- 

 bercles, lodged in areolae. The mouth is very eccentric, and the 

 buccal ambulacra are separated by swellings of the test. The vent is 

 infra-marginal and transversely ovate. 



It differs from Echinolampas ajffinis in ha\'ing a compressed (not 

 tumid) margin, in regularly declining with a gentle curve in its pos- 

 terior region, and in having its mouth much more eccentric. 



Echinolampas affinis?, Goldf. sp. [Not figured.] 



Pi. specimen of Echinolainpas, from the neighbourhood of Brussels, 

 was presented to Sir C. Ljell by Captain Le Hon, with the name of 

 Galerites ovalis ; this may, perhaps, prove to be the Clypeaster affinis 

 of Goldfuss. 



Echinolampas Dekini, Galeotti, sp. PI. VIII. fig. 2, a, 5, c. 

 This is the Galerites Dekini of Galeotti, pi. 4. 6, Suppl., fig. 10. 

 It is a good species, with a tumid test, much swollen throughout the 

 posteal region. Its apex is very eccentric. The petals are lanceolate 

 and not strongly marked ; the two postero-laterals are longest. The 

 tuberculation of the surface is equal and minute. The mouth and vent 

 are both transverse ; the former eccentric and lodged in a depressed 

 area, with tumidities surrounding it. The figure represents this spe- 

 cimen of the natural size. 



NucLEOLiTES APPROxiMATUS, Galcotti. PI. VIII. fig. 3, «, b, c. 



The specimen of this rare fossil is unfortunately in bad condition. 

 It appears to be a true Nucleolites and is exceedingly interesting, 

 since it is the only tertiary example of the genus with which I am 

 acquainted having an anal groove ; it thereby in some respects helps 

 to fill up the gap between the cretaceous Nucleolites of this division 

 and the unique existing Nucleolites recens of the seas of New Holland. 



Echinocyamus propinquus, Galeotti. PI. VIII. fig. 4, «, 5, c. 



This appears to be a good species, but in this genus it is very difii- 

 cult to find good characters. The position of the vent, away from 

 the margin, reminds us of the existing Echinocymmi,s pusillus. 



