o G4 SCHIZASTER FRAGILIS. 



the anterior and posterior both diverging more than is the case in S. cana- 

 liferus, and the posterior ambulacra are proportionally longer. The posterior 

 genital openings arc distant, the madreporic body well developed between 

 them, extending posteriorly. The peripetalous fasciole widens into a broad, 

 triangular space at the extremity of the anterior ambulacra, extends straight 

 across from tip to tip, the two posterior ambulacra making quite a re-enter- 

 in"- angle between the anterior and posterior lateral ambulacra. Lateral 

 fasciole running parallel to the ambitus. Outline of the test from above is 

 somewhat diamond-shaped, with rounded angles. Seen in profile, the test 

 tapers very gradually towards the actinostome posteriorly, regularly arched 

 to the anal system; posterior extremity abruptly truncated, receding below 

 the anal system ; the subanal fasciole runs in a curve under the anus in a 

 depression between the projecting cheeks of the adjoining ambulacral plates, 



a condition of things in striking contrast with the prominent keel formed 



at the extremity of the actinal plastron by the angular exterior of the sub- 

 anal fasciole in S. canaliferus. Actinal side flat, with broad ban' ambulacral 

 zones; actinal plastron elliptical, posterior extremity not well defined, losing 

 itself in the tubercles of the test under the subanal fasciole. 



Anal system covered by a large number of small plates carrying each 

 a small spine. 



The spines of the upper part of test are short, spathiform ; tuberculatum 

 larger towards the anterior extremity and near the ambulacra, size of spines 

 corresponding to this. The tubercles of the lower side are far apart near 

 the edge of the test and of the ambulacral zones ; those of the actinal 

 plastron are closely crowded, while adjoining the anterior groove they be- 

 come very prominent. 



The fragments of Schizaster found by Mr. Pourtales were referred to in 

 the Preliminary Report as Schizaster cubensis. Having since that time re- 

 ceived specimens of Schizaster fragilis from Dr. G. O. Sars and Professor 

 Thomson, there can be no doubt that the fragments belong to this species, as 

 they are the greater portion of the anterior part of the test. An examina- 

 tion of the original specimens of D'Orbigny's S. cubensis shows them to be 

 young Meoma ventricosa. 



Mr. Whiteaves has dredged specimens of this species in 250 fathoms in 

 the Gulf of St. Lawrence. 



80 fathoms, fragments. 



