ECHINANTHUS EOSACEUS. 313 



It is quite remarkable that of a species so common as this, only one young, 

 small enough to show any very striking difference from the adult, should 

 have been collected, while of nearly all the more common species complete 

 series of all sizes were obtained. 



This specimen is figured, natural size, on PL XP. f. 1. It is quite flat, 

 the actinal surface is concave, but the test is not yet swollen; in fact, the edge 

 of the test is only somewhat stouter than in some specimens of Clypeaster 

 subdepressus. The rosette is much smaller, with a dark median ambulacral 

 space, forming a prominent star, from the apical system ; the sutures of all 

 the plates are marked by similar dark bands, in both cases formed by minute 

 spines closely crowded together. The primary spines are comparatively 

 prominent, and are figured on PL XP. f. 14. They resemble already closely 

 those of the adult. Younger stages are represented on PL XP. f. 1..', 13, 

 the latter being still attached to the test, while the spine (/. W) has a distinct 

 articulating surface. Over the greater part of the upper and lower part of 

 the test are found pedicellariaj {PL XP. f. 6, 10) ; they are specially numerous 

 in the small triangle at the edge of the test in the median ambulacra (PL XP. 

 f. 3). These pedicellari* are peculiar ; nothing like them has as yet been 

 described, except those of Pourtalesia, which resemble them. They consist 

 (PL XP. f. (]) of a principal shaft, as stout and nearly as large as a primary 

 spine, more transparent, terminating in a cup from which arises a compara- 

 tively slender muscle, urn-shaped, terminating in a huge tridactyle head of 

 very remarkable structure, which terminates in three ball jaws ; each jaw is 

 broad at base, with from four to five roots, narrows rapidly to form a verti- 

 cal shaft, terminating in a hollow semi-spherical head, edged with strong 

 teeth (PL XP.f. s, 9), which magnified appear like a very formidable weapon 

 of attack. PL XP. f. 7 is another view of a similar pedicellaria. A second 

 kind is totally unlike this ; the head is spherical, made up of thin half-shells 

 articulated upon a lung slender muscle and a slender shaft (PL XP. f. 10). 

 The test when denuded (PL XP.f. 4) presents some striking differences from 

 the adult. The primary tubercles are not sunken, but are raised above the 

 general level, are comparatively few in number and large in size. The 

 sutures are well defined by close granulation, the median ambulacral space 

 being specially distinctly banded. In this stage the rosette is already de- 

 veloped (PL XP. f. 4), and from a denuded specimen would present no 

 special points of difference, except in size, from an adult, with the exception 

 of the absence of the genital plates, which are not yet developed, and the 



