74 SCHIZASTEE FRAGILIS. 



Schizaster fragilis Agass. 



Quite a common species near the 100 fathom line, off the Xew England coast. 71-362 fathoms. 

 For a list of Stations, see Bull. M. ( !. Z.. VIII. . No. 2, p. 84, 1880. 



PL XXVIII. Figs. 8-U. 



There is considerable variation in the distinctness of the lateral fasciole as 

 it passes under the anal system. In some cases it stops suddenly near the 

 level of the anal system: in others it can be faintly traced as an indistinct. 

 irregular anal fasciole ; in others the anal fasciole is most clearly marked. 

 These differences do not depend on size, but specimens from one locality are 

 usually similarly affected. Small specimens measuring 6 mm. in longitu- 

 dinal diameter are but slightly elliptical when seen from above, the anterior 

 ambulacrum scarcely indented, and the lateral ambulacra still flush with the 

 test. The actinal side is slightly convex, the outline seen in profile is 

 hemispherical, the apex being nearly central ; the circular anal system. 

 Hush with the test, is placed high on the posterior extremity of the test. 

 Both the peripetalous and lateral fascioles are well marked as narrow bands 

 of miliaries, indicating in a very rough way the future indentations of the 

 course of the fascioles. In this stage the posterior ambulacra consist only of 

 two pairs of pores, and are scarcely one epiarter the length of the anterior 

 lateral ambulacra. There is no trace as yel of any genital openings. The 

 actinal opening is circular, without a posterior lip, and the posterior edge 

 of the actinostome is placed nearer to the central part of the actinal side 

 than to the anterior edge of lite test. 



In specimens measuring 10 mm. in length, the posterior lateral ambulacra 

 tire still flush with the lot. with live pairs of pores ; the anterior ambulacra 

 are slightly sunken. The odd ambulacrum is more sunken than in the 

 younger stage described. The madreporic body, which in the preceding 

 stage was only pierced by a single opening, is now marked by live or six 

 small openings. There is as yet no sign of any genital openings. The 

 posterior extremity of the test is more vertically truncated; the anal system 

 is more elliptical, and placed at the upper angle of the posterior level of the 

 test. The fascioles are somewhat broader than in the younger stage ; they 

 vary in width, the angles of the ambulacra assuming more clearly already 

 ueral course they finally take in larger specimens. The actinal open- 

 now placed well towards the anterior extremity. The outline of the 



