REPORT ON THE ECHINOIDEA MORTENSEN 



283 



Genotype. — Psilocidaris echinulata Mortensen. 



Remarks. — This genus apparently stands midway between Gonio- 

 cidaris (subgenus Cyrtocidaris) and Aporocidaris, thus connecting the 

 latter with the goniocidarids. 



PSILOCIDARIS ECHINULATA, new species 



Plate 60, figs.l, 2; plate 61, figs. 4,5; plate 63, fig. 4; plate 73, figs. 3,4; plate 



78, figs. 3-5 



Localities. — Station 5127; Jolo (Sulu) Sea, in the vicinity of south- 

 ern Panay ; Nogas Island (W.) bearing N. 1 1 ° 30 ' E., 22 miles distant 

 (lat. 10° 02' 45" N.,long. 121° 48' 15 " E.); 1,751 meters; bottom 

 temperature 10.05° C; gray mud and globigerinae; February 4, 1908 

 (1 specimen, the type, Cat. No. E. 1334, U.S.N.M.). 



Station 5429; in the vicinity of eastern Palawan; Fondeado Island 

 (SE.) bearing N. 18° E., 15 miles distant (lat. 9° 41 ' 30" N., long. 

 118° 50' 22" E.); 1,400 meters; green mud; April 5, 1909 (spines 

 only, Cat. No. E. 1277, U.S.N.M.). 



Measurements 



Description. — The test is low, gently vaulted above, somewhat 

 flattened below, distinctly sunken toward the peristome. The sides 

 are beautifully arched; the circumference is circular. 



The ambulacra are rather distinctly sinuate. The interporiferous 

 zone is about twice the width of a pore zone. The marginal series 

 of tubercles is very regular; the tubercles are small and not contig- 

 uous. Within the marginal tubercle each plate carries a single tu- 

 bercle about half as large as the marginal one, which is situated at 

 the lower edge of the plate. There are thus four regular longitudinal 

 series of tubercles in the interporiferous zone, filling it up nearly 

 completely and leaving only a narrow naked sunken median line. 

 The horizontal sutures are without distinct grooves. The pore zone 

 is distinctly sunken; the pores are of about equal size, rather close 

 together, the narrow wall separating them being only slightly raised. 

 The ridge separating the pore pairs is narrow and only slightly ele- 

 vated (pi. 73, figs. 3-4). 



In the interambulacra the areoles are rather large, only slightly 

 deepened, and well separated; only the 2 or 3 small proximal ones 

 are confluent; even the lowermost ones are almost circular. The 



