270 VERRILL 



PTERASTER TESSELATUS HEBES Verrill. 

 Plate xcvi, figures I, 2 (type, enlarged). 

 Pterasler hebes Verrill, Amer. Joum. Sci., xxviii, p. 61, 1909. 



Disk plump and relatively large, the five rays being very short and 

 blunt, with the ambulacral grooves and plates turned upward and 

 reflexed upon the upper surface nearly to the base of the rays, or 

 about even with the shallow interradial angles. Radii, 22 mm. and 

 28 mm. ; ratio, i : 1.28. 



The central dorsal oscule is well developed, surrounded with 

 slender, webbed, projecting spines, in five groups of eight to ten each. 

 The dorsal surface is covered with a multitude of crowded slender 

 spinules, which project above the marsupial membrane and give 

 almost the appearance of velvet pile ; but in some places they form 

 more or less evident divergent stellate clusters of twelve to twenty 

 spinules. Seen from within, these spinules are slender, 2 mm. to 

 3 mm. long, very divergent, supported by slender columnar paxillas. 



The ambulacral grooves are broad and shallow. The ambulacral 

 plates are somewhat bilobed at the inner ends, and distally are some- 

 what imbricated. The adambulacral spines are long and slender, 

 about five or six in a transverse row, of which the two inner ones are 

 very small and slender, not half as long as the outer ones, of which 

 there are three or four, about 3.5 mm. long. 



The appressed actino-marginal spines are distinctly longer, about 

 twice as stout, and blunt proximally on the ray, but distally, on the 

 upturned part, where they are crowded, they become about equal in 

 length to the adambulacrals and scarcely larger; those near the 

 interradial angles are flattened and enlarged distally; the valves at 

 the peractinal pores between their bases are very acute, small, and 

 slender, as seen edgewise, but when removed they are acute-triangu- 

 lar, and curved proximally. 



Departure Bay, British Columbia, 23 fathoms, mud and sand, 1908 

 (C. H. Young, Canadian Geological Survey). One, dry and stuffed. 



The jaws and entire oral region have been destroyed by the pre- 

 parator. Therefore its relations to some of the other species are 

 uncertain. It seems to be nearest to P. tesselatus, of which it is prob- 

 ably only a variety ; some of the differences are probably due to imma- 

 turity. The mode of preparation and drying may have increased 

 the size of the disk considerablv. 



