190 PROF. P. M. DTJNCAT^'S EEYISION OP THE 



the ambulacral edges sunken, witb a rudimentary floscelle. Peri- 

 proct on tlie upper surface, in a groove commencing far from the 

 apical system, 



Fossil. Oolite; Europe. 



Genus Pseudodesoeella, Etallon, 1858-9, Etud. Pal. Saut. 

 Jura, pt. 2, p. 15. Desor Sf Be Loriol, 1868-72, Ech. Relvet. 

 p. 303. 



Test moderate, oval, broader than long, depressed. 



Apical system small, subcentral, slightly posterior, compact, 

 with four perforated basal plates and iive perforated radial plates ; 

 the madreporite extending backwards and touching the united 

 posterior radial plates. 



Ambulacra slightly petaloid, open, the poriferous zone narrow, 

 with the pairs above the tumid ambitus having an inner round 

 and an oater and somewhat elongate series, flush, continued as 

 round pores in pairs to the peristome. Tubercles numerous, 

 distant, perforated and with serobicules. 



Peristome nearly central, pentagonal, rather elongate, with a 

 moderate or absent floscelle. Periproct high up in a small short 

 groove, which touches the posterior radial plates, and enlarges 

 posteriorly. 



Fossil. Oolite : England, Europe. 



In the species of the genus EcMnblampas, Gray, 1825, there is 

 great variability of shape, size, and arrangement of the unequal 

 poriferous zones; but I cannot see the propriety of receiving 

 species into the genus which have equal 'poriferous zones. The 

 genus is a very large and natural one if it is properly restricted. 



Genus Echhstolampas, Gray, 1825, Ann. JPUl. p. 7 ; 1855, Gat. 

 Ech. Brit. Mus. pt. i. p. 34. Besor, 1858, Synopsis, p. 300. 

 A. Agassiz, 1872-4, Revision, pp. 335, 551. 



Test variable in size, more or less ovoid or circular at the tumid 

 marginal outline ; very variable in shape ; moderate in height, 

 tumid and vaulted above, very tall and conical or hemispherical, 

 depressed and more or less discoid. 



Apical system excentric in front, rarely subcentral, small, with 

 four perforated basal plates ; the madreporite large, in the right 

 anterior basal, and extending into the centre of the system, and 



