1884.] PROF. F. 3. BELL ON ECHINANTHTJS TUMIDUS. 41 



In this last statement I feel able to include the fossil forms, in a 

 review of which I was very greatly aided by the wide knowledge and 

 kind courtesy of Mr. Etheridge, F.R.S. 



I proceed first to give a detailed account of the specimen in my 

 hands, in connexion with which the careful figures may be suitably 

 studied. 



Description of the Specimen. — Test high, swollen, longer than 

 broad, flattened in the neighbourhood of the apical area, sloping 

 gradually at the sides, but sloping rather more sharply anteriorly 

 than posteriorly ; apical area a little anterior to the true centre of 

 the test ; anus exactly marginal, looking backwards and downwards, 

 and set almost exactly at an angle of 45° to the actinal surface of 

 the test. The actinostome deeply sunken, the five interambulacral 

 sutures only faint grooves. 



The poriferous zones very remarkable, being wider where they 

 terminate than at any otlier point along their course, and with a 

 faint tendency to be lyre-shaped. The pores vary very much in size ; 

 in the anterior (odd) ambulacrum the pores of the outer series are 

 easily seen only in the last fourth of the row, and here they are 

 large ; one row, that to the left of the specimen, has, however, only 

 one eighth of its course provided with large pores ; in the inner rows 

 the pores are smaller than the large pores of the outer rows, and a 

 larger number are subequal, the largest are at the distal end ; in the 

 left inner row there are a few scattered large pores near the proximal 

 end. In the right anterolateral ambulacrum there are no pores as 

 large as some of those in the anterior ; most of those in the two outer 

 rows are quite small, and in the inner some, though not so many as 

 in the anterior ambulacrum, are of fair size and subequal. In the 

 left anterolateral ambulacrum the outer rows have a few scattered 

 pores large enough to be seen without the aid of a magnifying glass, 

 near the apex ; in the inner rows the number of fair-sized subequal 

 pores is hardly less than in the anterior ambulacrum. The outer 

 rows of the right postero-lateral ambulacrum repeat very much the 

 characters of those in the anterior ambulacrum, and in the inner rows 

 there are a large number of fair-sized subequal pores. In the left 

 postero-lateral the pores are still better developed, and nearly both 

 members of every pair are quite distinctly seen ; as in the preceding 

 the larger pairs are in the outer rows. 



This predominance in the size of the pores of the outer row is a very 

 familiar phenomenon among the Clypeastridse. The grooves which 

 pass from pore to pore in every pair are shallow, and are almost as 

 well indicated by the row of tubercles which alternate with them ; 

 these tubercles are of fair size, twice as large as in Echinanthus 

 testudinarius, and there are, as a rule, five in each row ; they are 

 arranged in very regular parallel rows. 



Distally to the paired pores a pair, or two or three scattered pores 

 are to be observed, in the left half of the anterior ambulacrum, both 

 halves of the right antero-lateral and postero-lateral ambulacra, the 

 two halves of the left postero-lateral, and the anterior half of the 

 left antero-lateral ambulacrum. There is nothing, however, in the 



