ECHINANTHUS ROSACEUS. 311 



with the genital openings, which open in the interambulacral plates, its posi- 

 tion would seem to show that in the irregular Echini, where the anal system is 

 no longer enclosed by the abactinal system, the madreporic body can open 

 anywhere, and become connected with either genital plate, as in the Spatan- 

 goids, either right anterior or right posterior, or several of them, including 

 the left posterior, thus depriving it of the value which it has in denning the 

 bearing of the axis of the regular Echini, where its position is fixed, while it 

 is not fixed in the irregular Echini (isolated in the Clypeastroids, and may be 

 connected with any one of the genital plates in the irregular Echini), where 

 we find other features to guide us in placing correctly the axis of the 

 animal. 



Echinanthus rosaceus 



! Clypeaster rosaceus Lamk. 1816. An. s. Vert. 

 I Echinanthus rosaceus Gray, 1825. Ann. Phil. 



PL XI C . ; XI*. f. 1, 2 ; XI f . f. 1-18 ; XIII. f. 9. 



The characters by which most of the different species of Echinanthus 

 have been separated thus far are totally inadequate. The majority of the 

 large number of fossil species from the tertiaries have been distinguished on 

 variations of the height, breadth, outline, the more or less open ambulacral 

 petals, broader or narrower petals, — characters which the accompanying 

 measurements of a series of specimens from Florida show to be found in 

 any set of specimens from the same locality. The outline of this species is 

 more or less elliptical, with convex posterior, lateral interambulacra convex. 

 The test is usually moderately convex, varying in height from half to a third 

 the length of the longitudinal diameter. The ambulacral petals occupy the 

 greater part of the abactinal portion of the test, the madreporic body is 

 central, pentagonal, crowded with small tubercles, the intervening space rid- 

 dled with holes. The ocular plates joined to it are elliptical; the ocular 

 openings large. The genital openings are large, opening in the median inter- 

 ambulacral space at some distance from the madreporic body. The median 

 ambulacral space of ambulacral petals is broad, more than twice as broad 

 as the poriferous zone, the furrows of which are distant, of uniform breadth 

 for a considerable distance, and then diminishing rapidly towards the distal 

 extremity, and more gradually towards the abactinal pole. The tubercles 

 of upper part of test are remarkably uniform in size, sunken uniform 

 miliaries completely filling the intervening space. The tubercles are more 



