266 HAWAIIAN AND OTHER PACIFIC ECHINI. 



tively. The ocular plates are all broadly exsert in both specimens and they, 

 as well as the genitals, are somewhat swollen. The periproct is large, covered 

 by numerous small plates, among which a suranal can easily be distinguished. 

 The actinostomal membrane is thick, and carries few plates outside the buccal 

 circle. The buccal plates are thickly covered with pedicellariae but carry no 

 spines. The gill-cuts are shallow and poorly defined. The pedicellarise, sphseri- 

 dia, and spicules are essentially the same as in Alexandri. The globiferous 

 pedicellarise (PI. 93, fig. 32) have heads about .70 mm. long and are borne on 

 long, flexible stalks, 10-12 times as long as the head. The valves of the large 

 tridentate pedicellarise measure up to 1.75 mm. in length, and the blade contains 

 more mesh-work than in Alexandri. The spicules are bihamate. 



Echinus euryporus, 1 sp. nov. 

 Plates 93, figs. 2, 3; 109, figs. 4-6. 



The single specimen upon which this species is based is 46 mm. in diameter 

 and 26 mm. high. The test is well arched and the actinostome is not sunken. 

 There are 15 interambulacral plates in each column, and 26 ambulacrals. The 

 abactinal system is 12 mm. across, and the periproct is 15 mm. The ocular 

 plates are all broadly exsert. The periproct is covered by small but somewhat 

 swollen plates, among which the suranal can be easily distinguished. Each 

 interambulacral plate at ambitus carries, besides its primary tubercle, 8-12 

 secondaries and 50-60 miliaries. All the tubercles, even the miliaries, are 

 sufficiently elevated to be quite distinct and the test therefore appears rather 

 rough. In the ambulacra, the primary tubercles do not diminish uniformly 

 from the ambitus to the actinostome and abactinal system, but are of rather 

 unequal and irregular sizes. The poriferous area is moderately broad at the 

 ambitus, with the pores large and the arcs quite oblique. At the peristome, 

 the poriferous areas become decidedly widened, so that each one is wider than 

 the interporiferous area, and the arcs approach the horizontal. This feature, 

 upon which the proposed name is based, serves to distinguish euryporus from 

 any forms of acutus with which it might otherwise be confused, but it does not 

 assist much in separating it from elegans which resembles it in this particular. 

 The genital and ocular plates, except the distal tips of the genitals, are well 

 covered with small tubercles. The buccal membrane carries besides the small 



1 e'vpvs = broad + irdpos = a way. 



