716 



MR. H. L. HAWKINS OK 



[June 15, 



but its fellow on the left is imperforate. Thei"e are thus five 

 genital pores distributed over four of the genital plates. 



There are three ocular plates, corresponding with the termina- 

 tion of the three complete ambulacra ; each is perforated by a 

 minute pore. The ocular on the left is almost spherical in shape, 

 since it abuts against the middle of the large genital (3), and 

 not, as usual, against the two genitals (4 and 5). There is no 

 trace of the other two ocular plates. The periproct is covered by- 

 numerous irregular plates of small size. 



Text-fiff. 228. 



isr 



Apical s}'stem of an abnormal Ambli/pneustes. 



The composition of the interambulacral ar-eas (text-fig. 227, p. 71 5) 

 differs in the two afiected portions of the test. The two inter- 

 ambulacra 4 and 5 meet above the truncated end of ambulacrum Y, 

 and, except that the suture between the two areas is somewhat 

 irregular, continue side by side up to the apical system as a 

 compound area of four columns of plates. 



The adaptation of interambulacra 2 and 3 to the changed 

 conditions is different. Here column b of area 2, and column a 



