BY E. F. KALLMANN. 279 



spheres, which are equal in size to the centrum of the spherasters, 

 occur sporadically both in the choanosome and the cortex; though 

 few in number, they are not so rare as to excuse their being 

 overlooked; in rare instances, two or three spheres may occur 

 fused together. 



Although similar to one another in all the foregoing particulars, 

 the specimens are nevertheless of two forms in respect of a 

 number of other (spicular) characters. In one form, (i.)the rays 

 of the spherasters are rarely or never as long as (and usually are 

 somewhat less in length than two-thirds) the diameter of the 

 centrum, and not infrequently one or a few of them are provided 

 with a small spine or two (incipient branches), or are forked at 

 the extremity; (ii.)the tylasters, which may attain to 19/x in 

 diameter, have short stout rays usually less in length than the 

 diameter of the centrum and provided with a well -developed 

 terminal knob densely covered with minute spines; and (iii.) the 

 oxyasters, which vary from (seldom) 20 fx to 35 /x in diameter and 

 are fairly abundant, have moderately stout rays (1-5 to 3 /x in 

 diameter near their base) with the distal half of their length 

 covered with well-developed tubercles. In the other form, (i.)the 

 rays of the spherasters are generally as long as, or slightly longer 

 than, the diameter of the centrum, and rarely (if ever) exhibit 

 incipient branching; (ii.) the tylasters are at most 17/x in 

 diameter, and have comparatively slender rays, which are longer 

 than the diameter of the centrum, and are usually only slightly 

 knobbed, and which are provided with spines, not only around 

 their extremity, but also for some short distance along their 

 length; and (iii.) the oxyasters, which are of about the same 

 diameter as those of the preceding form, have slender ravs only 

 sparsely provided with tubercles. 



Remarks. — Among the fragments received from the British 

 Museum, there is one labelled Tethya phillipensis which, in 

 skeletal characters (excepting that the spherasters are at most 

 only about 55 /x in diameter), is in various respects intermediate 

 between the two above-described forms. Unfortunately this 

 fragment was used up in the preparation of sections from it, 



