74 VERRILL 



portion of smaller to greater diameter, i : 3.5. Ambulacral furrows 

 broad at the base of the ray, where the pores are crowded into six 

 rows. Ambulacral spines in one regular row, slender, compressed; 

 subcylindric, as long as the ventral spines, somewhat tapering, with 

 bluntly-rounded tips. Ventral spines crowded, very numerous, in 

 six or seven rows near the base of the ray ; short, subcylindric, a little 

 bent outward, and slightly flattened externally, with more or less 

 longitudinal striation near the tip. Beyond the ventral spines there 

 are no regular channels, but the surface is covered with pedicellariae 

 and minute spines. The dorsal spines are numerous, equal in size, 

 but very small, — not more than one-twentieth of an inch in length, 

 scarcely capitate, but more or less pointed. They are uniformly dis- 

 tributed over the disc and rays in a reticulating manner, the inter- 

 spaces being from one-tenth to one-half inch in diameter, and 

 thickly crowded with groups of papulae and minor pedicellariae ; the 

 latter generally occurring about the bases of the spines, but not 

 forming wreaths or crowns. The major pedicellariae are very short 

 and stout, regularly conical or somewhat wedge-shaped, with very 

 broad valves. They are very numerous, particularly on the disc, 

 where they often stand in groups of ten to twenty together. The 

 largest are found isolated in the angles of the rays below, where one 

 occurred having a diameter of eight-hundredths of an inch, and a 

 regularly conical form, with a square base. Diameter of our only 

 specimen, ten inches. 



" It is allied to A. ochracea, but differs in its more numerous 

 spines, pedicellariae, and ambulacral p»ores. 



" Habitat, Puget Sound — North West Boundary Commission. Dr. 

 C. B. Kennedy." 



I have reproduced large photographs of the type of this species, 

 now in the National Museum. These were sent by Dr. R. Rathbun. 

 (See pi. XXXVIII, figs, i, 2, reduced.) 



In this specimen the radii are about 45 mm. and 162 mm. ; ratio, 

 about as i : 3.6. The rays are thick at base and taper rapidly, though 

 they differ considerably in this respect, indicating that the skeleton 

 in life is rather flexible and weak. The crowded six-rowed or eight- 

 rowed arrangement of the proximal ambulacral pores is very evident. 

 The slender adambulacral spines near the mouth are much longer 

 than those farther out, as in some other species ; they stand singly 

 on the plates, in one regular row. The ventral spines are pretty uni- 

 form in size and form, and are nearly smooth and blunt ; they stand 

 mostly in six rows proximally, but form only four or five rows at the 



