11 2 



ECHINANTHUS KOSACEUS. 



closely set in the median part of the ambulacral petals than upon rest of 

 test. This median part is frequently quite swollen, rising far above the gen- 

 eral level of the test, so that the poriferous zone is regularly sloping from the 

 edge of the zone to the interior row of pores ; there the test rises suddenly, 

 and is regularly arched over the remainder of the median ambulacra] space. 

 On the lower side, in old specimens, the mouth is deeply sunken, the cavity 

 in which it is placed forming quite abruptly at about two thirds the distance 

 from the edge of the test. The ambulacral furrows are very plainly defined, 

 increasing rapidly in width a short distance from the edge of the test, and re- 

 taining a uniform breadth to the mouth. The tubercles of the lower side are 

 much larger than those of upper part of test, placed closer, more deeply 

 sunken, the miliaries surrounding them not so distinct. The anus is placed 

 close to the edge of the test. The spines are short, of uniform size over 

 the whole upper part of the test with the exception of the poriferous zone, 

 where the average of the spines separating the ambulacral furrows is some- 

 what moii' slender. Those of the lower part of test are considerably stouter 

 and longer than those of the upper part of the test. 



The posterior ambulacral petals are the longest ; the odd ambulacral one is 

 slightly shorter, the anterior pair are considerably shorter; the median space 

 of the odd petal is narrower than that of tin' other ambulacra, which are of 

 uniform breadth. 



The color of this species when alive is. from above, a beautiful reddish- 

 brown; the median ambulacral region enclosed by the poriferous zone is more 

 yellowish ; the poriferous zone, of a darker reddish color, is a background 

 upon which the flesh-colored lobed tentacles of the pctaloid ambulacra are 

 projected (PL Xl r .f. 17, IS). The whole upper part of test is also covered with 

 minute flesh-colored water-tubes, capable of considerable expansion, passing 

 through the small pores which riddle the whole of the test of these double- 

 walled Clypeastroids. 



Littoral t" •"> liitlioms. 



