Boone, Echinodermat a, Cruises of "Eagle" and "Ara," 1921-28 145 



SCUTELLIDAE. 



Genus: ECHINARACHINUS Leske. 

 Echinarachinus parma (Lamarck). 



Plate 93 and text figure 6. 



Name: Sand Dollar. 



Type: Lamarck states of his type, "Habitat 1 'Ocean des Indes. Mon 

 Cabinet." This cabinet was later placed in the Paris Museum. 



Distribution: This species has a very wide distribution, being 

 found on the American Atlantic coast from Labrador to southern 

 New Jersey and on both American and Asiatic shores of the Pacific ; 

 on the American Pacific coast it ranges from the Aleutian Islands 

 down to British Columbia, and on the Asiatic shore southward to 

 Japan. In the more northern localities it is found inshore, near the 

 low-water mark, while farther south it inhabits deeper water. It has 

 a recorded bathymetric occurrence from the tide-line down to 800 fms. 



Material examined : Three specimens, Eastport, Maine, August 24, 

 1924, Cat. no. 293. Four specimens, from the estate, Northport Har- 

 bor, Long Island Sound, Cat. no. 294. 



Habits: This odd urchin is one of the group which has its body 

 exceedingly flattened and modified in order to enable the animal to 

 meet the requirements of its environment. It lives on sandy bottom 

 off shore, partly buried beneath the surface of the loose sand. It feeds 

 on the minute organisms, especially diatoms and other algae, found 

 among the sand which it ingests. The disk-like body enables it to 

 withstand its being upset or displaced by the shifting of the sand 

 under the influence of the waves. 



Color: In life the larger adults are reddish brown or purplish 

 brown, while the smaller adults are paler red. 



Technical description : Test exceedingly flattened, disk-like, nearly 

 circular in outline but slightly indented at one point, indicating the 

 anus. Test closely covered with minute spines, which are nearly 

 uniform on the abactinal surface, longer on the margin, but longest 

 in the interradial areas at the peristome. On the abactinal surface 

 the slenderer, ambulacral areas or "petals" are placed symmetrically 

 around the central plate and are well defined by the position of the 

 respiratory tube-feet. The petals are widely open, somewhat obtuse, 

 extending three-fifths of the distance to the margin. On the flattish 

 actinal surface the ambulacral areas are marked by furrows, which 



