ECHINARACHNIUS PARMA YAH. OBESA. 67 



constant. The pedicellariae are reduced in both number and size. All have 

 two valves. The bidentate are remarkable for the more or less complete lack 

 of apophyses, while the biphyllous are very small indeed and of rather an odd 

 shape (PI. 125, fig. 7). There are no calcareous disks or rings in the pedicels 

 but each sucker is strengthened by a pair of calcareous rods, somewhat bent, 

 lying with their concave sides towards each other and with an outstanding spine 

 on the convex side. After the examination of hundreds of specimens, it has 

 seemed desirable to recognize three species and one variety. 



Key to the Species of Echinarachnius. 



Actinal ambulacral furrows branching only near distal end. 



Test variable in height but not remarkably thick and solid; color in life reddish brown 

 of some shade, often very light, becoming green in alcohol and drying green or 

 brown often very dark; abactinal primary spines not conspicuously thickened 

 near tip. 



Test low and flat, v. d. .11-. 18 test-length parma. 



Test high, sometimes more or less conical, v. d., .17-.25 test-length . . . parma var. obesa. 

 Test high, v. d. = .18-.25 test-length, and remarkably thick and solid; color in life un- 

 known; alcoholic and dry specimens similar, more or less strongly violet, especially 

 on oral surface, but primary spines whitish; abactinal primary spines remarkably 



swollen near tip asialicus. 



Act inal ambulacral furrows forking proximal to middle mirabilis. 



Echinarachnius parma. 



Scutella parma Lamarck, 1816. Anim. sans Vert., 3, p. 11. 

 Echinarachnius parma Gray, 1825. Ann. Phil., 26, p. 428. 



Plate 125, figs. 7, 8. 



This is the common sand-dollar of the East coast of North America, from 

 New Jersey northward at least to Labrador. Apparently it occurs on the West 

 coast also from Alaska as far south as Puget Sound. On the Asiatic coast it is 

 represented by the following variety, which also occurs along the Alaskan 

 Peninsula. 



Echinarachnius parma var. obesa, 1 var. dov. 

 Plate 143, figs. 5-8. 



Similar to E. parma except that the test is remarkably high, the vertical 

 diameter often one fourth of the test-length. Extreme examples are so unlike 

 the ordinary parma, one is tempted to consider them a distinct species raid Mr. 



1 obesus = fat, in allusion to the plump test. 



