26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



posterior to it. A live specimen is white with very short spines and 

 red tube- feet. Most of the specimens are small, around 30 mm. long, 

 elongate, with narrow, simple poriferous zones, and small, equal-size 

 tubercles. The species occurs with Brissus unicolor, from which it is 

 easily distinguished by lack of petals, lower test, shorter spines, 

 oblique peristome, and position of periproct near the peristome. 



Occurrence. — Dead tests of Echinoneus cydostomus were found 

 on the sand below Molasses Reef and Grecian Rocks, among debris 

 eroded from the reefs. These occurrences are well offshore, in depths 

 from 20 to 40 feet. Mortensen (1948, p. 78) reports that this species 

 lives among slabs of rock, normally clinging to undersur faces, and 

 eats organic material adhering to rather coarse grains of sand and 

 shell fragments. It has been found in waters as deep as 350 feet. 



We found few living specimens of this species ; these did not seem 

 to be clinging to the undersurfaces of rocks, but appeared to be living 

 in coarse sand beneath the rocks. Unfortunately, the surge of waves 

 removed the specimens from their habitats as soon as the rocks were 

 overturned, so it was not possible to observe the echinoid in place. 



Dead tests were found at stations 19 and 43, living specimens at 

 station 60. 



Order Clypeasteroida Agassiz 

 Family CLYPEASTERIDAE Agassi/ 



Genus CLYPEASTER Lamarck 



CLYPEASTER ROSACEUS (Linnaeus) 



Plate 4, figures 1-7; plate 6, figure 7; text figure 6 



The test of a living specimen is dark brown, elongate, with inflated 

 petals of equal length. An adult is approximately 130 mm. long, and 

 is deeply invaginated around the mouth. Locally, this species is 

 called a sea biscuit. It is a distinctive species and is easily dis- 

 tinguished from Clypcaster sitbdepressus, a species often occurring 

 near it, by its much higher test, impressed mouth, and darker color. 



Occurrence. — Clypcaster rosaceus lives in areas of thick sand, 

 either in grassy areas or on relatively grassless patches within grassy 

 areas. It is most characteristically associated with Lytechinus variega- 

 tus and Tripneustes ventricosiis in the turtle grass, but also was found 

 commonly with Clypcaster subdepressus and Meoma ventricosa in the 

 cleaner sand areas near grassy patches. Its range extends from near 

 shore to just inshore from the main body of the reef, and some speci- 



