50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



were dissolving spines and the test of the urchin. Previously, many 

 specimens had been observed with large or small areas that were free 

 of spines, and which, as a consequence, were but poorly covered by 

 sand (pi. 11, figs. 2, 3). Later examination of specimens in the lab- 

 oratory showed others, each with the spineless area stained a brown- 

 ish purple where the digestive fluids of the starfish had been active. 

 Apparently M. ventricosa is a frequent victim of O. reticulatus. Some 

 individuals obviously were able to escape alive, but with some portion 

 of the test stripped of spines. 



Several specimens of M. ventricosa with bare areas devoid of spines 

 were observed at station 21. These lay buried just below the surface 

 of the sand, and the spineless areas remained uncovered by sand. A 

 small fish, identified by J. E. Randall as the red band parrot fish 

 Sparisoma aurofrenatum (Valenciennes), was seen to swim to the 

 urchin and nip at the exposed areas. Some of the specimens were 

 dug up and placed on the surface of the sand, and the parrot fish 

 photographed as it nipped them (pi. 11, fig. 1). The spineless areas 

 in these specimens differ from those in which the spines had been 

 removed by dissolution by Oreaster reticulatus. No spines were partly 

 dissolved, or "thinned" as in a second specimen taken from station 23 

 where the starfish was observed in process of attacking an urchin, and 

 there was no sign of partial dissolution of the test. Furthermore, the 

 depressed petalous areas retained their spines, and only the highly 

 convex areas between petals were denuded. Possibly these are speci- 

 mens that were attacked by O. reticulatus, but made good their escape, 

 with the fish then taking advantage by nipping at the areas that lacked 

 spines and therefore were not covered by sand. However, the differ- 

 ence in the bare areas, cited above, suggests that they were due to the 

 grazing of the fish. 



Family SCHIZASTERIDAE Lambert 



Genus SCHIZASTER Agassiz 



Subgenus PARASTER Pomel 



SCHIZASTER (PARASTER) FLORIDIENSIS Kier and Grant, new species 



Plate 13, figures 4-6; plate 14, figures 1-9; text figure 15 



Diagnosis. — Species characterized by central apical system, narrow 

 ambulacrum III, and flexuous anterior petals. 



Material. — Four denuded tests, one incomplete specimen with 

 spines. 



