i4 Bulletin 26 98 



NUCLEOLITIDM 



Genus Echinobrissus, Breynius 



Echinohrissus angustatus Clark 



Plate VII, figures 6-9; Plate IX, figure 4 



Echinobrissus angustatus Clark, 19 15, U. S. Geol. Survey Monograph,, 

 Vol. LIV, p. 69, Plate XXVII, figs. 2a-c. 



Dimensions. — Length, 15.5 mm.; width, 14 mm.; height, 

 8.5 mm. 



Description. — Test small, subovate, rounded anteriorly, 

 subquadrate and broadest posteriorly; upper surface elevated; 

 apex anterior of the centre; lower surface concave. 



The ambulacral areas are subpetaloid on the upper surface, 

 simple toward the ambitus, and form a rudimentary floscelle 

 near the peristome. The posterior ambulacra are the longest. 

 Between the pore zones the areas are ornamented with two 

 alternating rows of mammillated, perforate tubercles whose 

 areolas are deeply sunken and surrounded by closely set granules. 



The pores within the subpetaloid parts are arranged in pairs, 

 the outer pores of which are oval whereas the inner ones are round. 

 Here the pore pairs are separated by rows of fine granules, four 

 to the row, within the pore zone itself. From the open ends of 

 the subpetaloid parts the pores are fine and continue in diverging 

 single rows to the ambitus. On the lower surface the pores again 

 become paired and obliquely set in the floscelle. 



The interambulacral areas are broad and ornamented with 

 numerous tubercles surrounded by deeply sunken areolas. The 

 spaces between these areolas are covered with fine granules. 



The apical system is small. Four of the genital plates are 

 pierced by large genital openings. The madreporite is large and 

 centrally located. 



The peristome is subpentagonal, sunken and ornamented 

 with several rows of fine, closely set granules. 



The periproct is oval, and situated at the anterior end of a 



deep groove. 



Although the material described by Clark was too poor to 

 serve as a basis of a satisfactory description, it appears to be the 



