66 THE FOSSIL ECHINOIDEA 



rounded anterior margin. The posterior part of the test above, is flatter than the 

 anterior. 



The peristome is under the apical system, and is slightly in front of the centre. 

 The periproct is supramarginal, in a deep groove, which slightly flattens out posteriorly, 

 where it terminates at the truncated end of the test. It is narrow and longitudinal, 

 nearly vertical, and under the overhanging test ; and its position is considerably behind 

 a line which would unite the extremities of the posterior petals. 



The apical system is small ; the four generative pores are distinct ; and the madre- 

 poric body, which does not extend backwards to separate the posterior ocular plates, is 

 well developed and central. The ambulacra are petaloid, and the antero-lateral and 

 posterior are nearly closed ; the anterior ambulacrum is the broadest, and the posterior 

 are the largest. The ambulacra are broadest in their apical half, and the zones are 

 well developed ; but the posterior poriferous zone of the posterior ambulacra is slightly 

 smaller, especially near the apex, than the anterior zone of the same ambulacrum. 

 Otherwise the poriferous zones are well developed, and one of them is nearly as wide 

 as the interporiferous zone is broad. 



The poriferous zones are nearly flush with the test, and the numerous conjugate 

 pores are separated by distinct costal elevations ornamented with a single row of 

 granules. The inner pores are more or less circular in outline, and the outer are 

 smaller and more elongate ; and the direction of the conjugate grooves is oblique. 

 The poriferous zones of each ambulacrum are equally bent. The interporiferous 

 zones are very slightly raised, are ornamented with numerous tubercles standing in 

 sunken scrobicules, and which are slightly smaller than those in the interambulacral 

 spaces. 



The ambulacra do not reach near the margin ; and the end of the posterior is ^s 

 inch from the posterior end of the test, the periproct being -^g inch from the same part. 

 The interambulacra are well rounded off"; but there is a faint keel between the posterior 

 lateral, which reaches backwards to the periproct. The ornamentation of the interradials 

 is small on the apical surface of the test, and gradually increases in size at the margin ; 

 it consists of small tubercles in sunken scrobicules, with the intermediate area or 

 ridge covered with minute granules. 



The peristome is slightly longest longitudinally, is large, pentagonal, and the 

 floscelle is highly developed. The bourrelets are granular and swollen, with tubercles 

 on the lowest projecting point ; and the buccal pores are in nearly closed phyllodes, 

 which are petaloid and broad. The reduplicate pores are numerous ; and there are 

 two sets of depressions for sphseridia along the interporiferous line. 



The ornamentation of the actinal is much larger than that of the abactinal surface, 

 and the tubercles are often placed on one side of their scrobicule and close to the 

 intervening ridges. The large tubercles are seen along the lines of the ambulacra 

 beyond the phyllode ; and close to the edge of the test all the ornamentation becomes 

 suddenly small. A cancellated and worm-eaten tract extends in the median line from 

 the moutli to close to the truncated margin, and it is also seen in front of the peristome. 

 It appears to be produced by confluence of granules. 



