ECHINOBRISSUS. 555 



goids proper, but they have the same ornamentation as those of the upper side 

 of the test. The ridges separating the pits round the larger tubercles of the 

 actinal side are irregularly studded with minute tubercles, carrying small 

 spines like those of the median band. Similar tubercles are irregularly 

 scattered on the ridges between the primary tubercles of the upper surface, 

 carrying slender, silk-like miliary spines. The transverse crescent-shaped 

 anal opening is protected by a membrane covered by a posterior row of 

 four large polygonal plates, with a second row of five or six smaller ones, 

 and an irregular minute row at the edge of the membrane next the anal 

 opening ; this is an elongated slit placed near the upper part of the anal 

 system, directly under the projecting ridge of the test. 



The greatest diameter in smaller specimens is in front of the anus, while 

 in older specimens it is anterior to the apical system. The inner pores of 

 all the poriferous zones are round, joined by a shallow furrow to the outer 

 larger comma-shaped pores, which extend, irregularly scattered, from the 

 termination of the petals towards the actinostome, where they meet the 

 phyllodes. 



The color in alcohol is greenish-yellow, mottled with darker spots, but 

 slightly darker than the light greenish-yellow tint, similarly spotted, of life. 

 This species lives like other Spatangoids of which the habits are known, — 

 gregariously on sandy beaches, from five to six feet below low-water mark, 

 half buried in the sand up to the extremity of the petals. 



Galapagos ; Panama ; Gulf of California. 



ECHINOBRISSUS. 



Echinobrissus Breyn., 1732, Schediasm. de Echin. (pars.) 



Test rather flat, elongate, subquadrate, wider at posterior extremity, 

 more or less convex above, concave below. Ambulacral petals somewhat 

 lanceolate ; poriferous zones narrow ; pores not conjugate. Vertex eccen- 



