549 



with 2 unequal spines. Adambulacrals with 5 or 6 subequal furrow 

 spinelets and 2 actinal spinelets. R 100 mm; r 15 mm; R 6,6 r. Breadth 

 of ray at base, 17 mm. 



Off Prince of Wales Island, British Columbia, 1569 fathoms. 

 Bottom, gray ooze. 



Acantharchaster Verrill. 

 Syn. Mareellaster, Koehler, Zool. Anz. Bd. XXXII. 1907. 144. 



Related to Benthopecten\ odd interradial marginal either absent, 

 or present in only a part of the interradii ; abactinal plates (of disk at 

 least) tabulate, the larger bearing a conspicuous central spine surrounded 

 by a circle of more or less elongate spinelets. 



In this genus the primary abactinal plates of the papular region 

 are either stellate with numerous lobes, or roundish with faint indication 

 of lobing. The plates are raised into a low tabulum bearing a variable 

 number of spinules, and a central movable spine. 



The following species, all but the first new, occur off the west coast 

 of North America. 



a. No odd interradial marginal plates; R, less than 6 r; 



abactinal plates not stellate on papular area A. dcnvsoni Verrill. 

 aa. Odd interradial marginal plates; R, more than 7 r; 

 abactinal plates stellate on papular area. 



b. Papulae extending far beyond middle of ray ; dorsolateral 

 musclebands inconspicuous; marginal mouth spines 10 

 or more , not graduated in length toward the inner 2 

 which are abruptly larger. 



c. Abactinal accessory spinules long and slender forming 



with the primary spines a dense armament; secondary 

 plates with long spinules, furrow spinules 1 to 3. 



A. acicidosus new species. 



cc. Abactinal accessory spinules not greatly developed, in 

 length or number; if developed at all only 2 or 3 around 

 each spine: secondary plates with short spinelets; 

 abactinal integument firmer and plates closer together; 

 furrow spinules 4 to 7. 



d. Numerous abactinal pectinate pedicellariae together 

 with inferomarginal and actinal intermediate pedicel- 

 lariae. Disk larger . . A. variabilis pedicellaris new subspecies. 



dd. Very few abactinal pectinate pedicellariae, and only ex- 

 ceptionally actinal or inferomarginal ones. Disk smaller. 



A. variabilis new species. 



