174 Bulletin Vanderbilt Marine Museum, Vol. VII 



meters behind the anterior margin. The test is very fragile, oval, 

 wider anteriorly, the sides low but with the abactinal surface very 

 gently elevated posteriorly, attaining the greatest height at about 

 the center of the apical system, behind which point it slopes briefly 

 to the rather abruptly truncate posterior area. The abactinal sys- 

 tem is slightly posterior to the center of the long diameter. The 

 madreporite, of irregular shape and perforated with more than 

 a hundred apertures, has a narrowed portion extended anterior 

 to the apical center and obliquely toward the right lateral petal 

 but the major portion of the madreporite extends posteriorly, 

 more to the right than central and is irregularly suboval, with 

 the posterior margin subtriangular and separates the posterior 

 genital and ocular plates. Three genital pores are present, one 

 on the right side near the anterior of the wider part of the madre- 

 porite and two on the left side, near to each other, and the anterior 

 one is about opposite that on the right side. (Plate 67, fig. g). There 

 is a rather deep notch in the frontal margin caused by the frontal 

 ambulacrum. Petal III is 40 millimeters long and 9 millimeters 

 wide anteriorly, moderately sunken ; distally it is sunken into the 

 frontal margin, incising this and with the depression extending 

 almost to the narrowed, projecting labium. The anterior paired 

 petals II and IV are divergent, as shown in plate 65, shallow, dis- 

 tally rounded, each being 32 millimeters long and about 6.5 milli- 

 meters wide near the tip. The short posterior paired petals, I and 

 V, are not quite five-eighths as long as the preceding pairs, II and 

 IV, being only 17.5 millimeters long and quite shallow. The peri- 

 petalous fasciole is very distinct, quite narrowed and sinuate, but 

 wider than the lateroanal fasciole, which is traceable in its entire 

 course in the three largest specimens but is somewhat indistinct 

 on the smaller ones in the lateral portion. The sternum, from the 

 tip of the labium is 45 millimeters long and about 15 millimeters 

 wide, closely covered with smallish tubercles ; in the larger speci- 

 mens it is definitely keeled, as well as projecting. (Plate 66) . 



The spines are of two kinds ; one of the larger kind, which are 

 most abundant along and overarching the petals, have the pattern 

 shown in plate 67, figure a, the collar being striated, the shaft 

 being smaller proximally, subcylindrical, gradually dilated and 

 laterally compressed distally, with the apex widely rounded, the 

 distal portion being spatulate ; there are eighteen to twenty longi- 

 tudinal ridges, each composed of fine asperities, extending the 



