516 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



stomach, and dextrally coiled intestine. The closure of the orals has compressed 

 the mouth of the esophagus so that its margin appears crenulate or folded. 



There are two specimens in which this stage is distinctly shown. In the second 

 the orals, while of the same relative size as in the one just described, are slightly 

 parted, and the oral tentacles project between their summits, but have not yet 

 branched. As in the first, the radial of the right posterior ray has not appeared, 

 but its place is occupied by the radianal attached to the gut. Although the pro- 

 jecting tentacles make this specimen appear the more advanced, the radianal is 

 smaller than in the other one. The difference is due to the slight opening of the 

 orals, which stretches the mouth so that its border is without wrinkles. 



In the next stage represented the right posterior radial has appeared, and 

 beneath it to the left is the rapidly enlarging radianal attached to the gut, which 

 is still visible through the thin reticulate plates of the body wall just below the 

 anal opening. The disparity in size between the two plates is important, as tend- 

 ing to confirm the antecedent appearance of the radianal and its status as an 

 independent element. The anal pore is here verj' distinct, and the intimate attach- 

 ment of the plate to the gut just below the opening is evident. 



In the following stage the radials have notably increased in size, and above 

 them at the base of the tentacles may be seen two small disconnected plates which 

 are the beginnings of the IBr^ and IBr„. The radianal is enlarged to a lesser 

 degree, and it lies to the left of the radial, which now begins to curve around it 

 toward the middle of the posterior basal. The gut has become concealed behind 

 the radianal excei^t at the opening, which is visible at the apex of that plate. 



In the next stage the radials have enlarged until thej^ almost come into lateral 

 contact, except posteriorly. The elements of the IBr series have thickened and 

 become connected with the radial and with each other, the IBr, being an axilliary 

 and covering the base of the tentacles, now three in number. The basals and 

 orals have become relatively smaller, owing to the superior gi'owth of the radials. 

 The radianal is approximately on a level with the radial to the right of it, indent- 

 ing its left side and still touching the sloping shoulders of the posterior basal. 

 In the triangular spaces between the radials and orals small plates have appeared, 

 formed in the same manner as the other calyx plates, which are readilj' recognized 

 as interradials. The orals now exhibit rather distinct pores distally. 



In the following stages the radials increase in size until they greatly exceed 

 the basals, which now form a low and nearly horizontal base. The interradials 

 are pushed upward through the meeting of the radials below them and increase 

 in number from one to five or six, in the posterior interradial area passing over 

 into the plates of the heavily plated integument which is extended upward into 

 a large conical protuberance now definitely constituting the anal tube. The gut 

 has continued to extend itself upward until its opening is now at the apex of 

 the conical projection rising far above the orals, which by the multiplication 

 of interbrachial plates are now being more and more separated from the dorsal 

 cup and are becoming relatively reduced in size. The radials have met and have 

 formed a closed ring. The arms have appeared, and rudimentary cirri have 

 appeared upon the proximal columnal. All the elements of the comjilete skeleton 



