246 Bulletin Vanderbilt Marine Museum, Vol. VI 



plate of the abactinal skeleton. These plates are rather widely 

 spaced, forming a coarsely meshed skeleton. The actinal primary 

 spines are skin encased, regularly, evenly granulated for practi- 

 cally their entire length. The primaries are 20 to 30 mm. long, 

 including the pedicel, which measures from one-fourth to one- 

 third of this total length. These primaries are longer and some- 

 what more numerous towards the circumference of the disk. 

 Again about midway the length of the rays these spines average 

 the greatest length to be found on the dorsal surface. The pri- 

 maries of the center of the disk average 20 mm. long and those 

 of the middle arm average 30 mm. long. The abactinal surface 

 of the disk, the proximal half of the abactinal surface of the rays 

 and two-thirds or more of the dorso-lateral surface of the rays, 

 bear numerous secondary or young spinules from 1 to 4 mm. in 

 height, each of which arises from a miniature pedicel. The papu- 

 lar pores are fine and closely grouped. There are five small, round- 

 ish, wartlike madreporic bodies present on the disk, four of which 

 occur within a radius of one-half of its circumference. The 

 abactinal pedicellariae are very characteristic, being very slender, 

 with their jaws from three to six times longer than wide. 



The actinal surface has the spines moderately coarse, rather 

 regular, individual spines vary from entirely finely granulated 

 to being partly finely granulated, with the remainder nearly or 

 quite smooth. The furrow spines are normally three, of conspicu- 

 ous size, acuminate, the central one usually being the longer. There 

 is usually a short, stub-like spinelet present, at one or both ends 

 of each furrow series ; sometimes the adoral spinelet is replaced 

 with a short, bluntish, moderately tapered, two-jawed pedicel- 

 laria. The greater percentage of the plates have, located on the 

 furrow face of the plate, near the adoral margin of the plate, a 

 rather conspicuous, slender, tapered, two-jawed pedicellaria, most 

 frequently located so that the jaws are respectively dorsal and 

 ventral. The subambulacral spines average about three to three 

 and one-half adambulacral plates in length and have a rather regu- 

 lar size. Each spine is grooved on the outer side of its distal third 

 or half. The actinal intermediate spines are similar to the sub- 

 ambulacral spines. The slenderer of these spines are usually less 

 prominently grooved. 



References: Asterias planci, Linne, C, Syst. Nat., ed. X, 1758, 

 p. 823. — Linne' quotes Columna, Phytobasanos, pi. 33, fig. 



