220 J. H. ORTON. 



The collar of C. saxicola is relatively delicate, that of C. normani 

 relatively stout. In specimens of the two species of about the same size, 

 both the radials and interradials in C. normani are stronger, wider, and 

 longer than in C. saxicola. (See Figs. 4 and 5.) In the latter species the 

 interradials are deeply bifurcated at the posterior end (see Fig. 4), 

 whereas in C. normani these plates are only slightly bifurcated (see Fig. 5), 

 and the radials of C. normani differ from those of C. saxicola in being 

 deeply constricted at the sides near the posterior end. Further, in 

 C. saxicola there is a long narrow calcareous connecting loop between the 

 radials and interradials, whilst in C. normani the similar connecting 

 pieces are short and stout and produced posteriorly to a point. Hence 

 the collar of C. saxicola is doubtless capable of much greater expansion 

 than is that of C. normani. The shapes of these collars can be easily 

 seen in preparations made by first soaking the anterior end of the animal 

 in glycerine and afterwards dissecting away the surrounding tissue and 

 mounting the collar in glycerine or glycerine jelly. This was found to 

 be a better method than treating the collars with potash. 



CHAKACTERS OF THE SPICULES AND TUBE-FEET IN 

 C. SAXICOLA AND C. NORMANI. 



The characters of the spicules in C. saxicola have already been well 

 described by Brady and Robertson (4). These characters have been 

 confirmed by De Morgan (loc. cit.) and the present writer. They have 

 also been found to co-exist with the characters of the gonad and cal- 

 careous collar given above for the species. 



The spicules of the adult C. normani have also been well described 

 and figured by Norman (2 and 3, Plate XI, Figs. 1, 2, 3, and 4) from his 

 specimen labelled A. Spicules identical with these have been found to 

 be correlated with a gonad consisting of a large number of small tubes 

 and a calcareous collar as described above. 



It is therefore only necessary here to point out the main features of 

 difference between the chief kinds of spicules occurring in these two 

 forms. The chief body spicule in C. saxicola is plate-like and rhomboidal 

 in outline, having the opposite ends of one axis more or less produced. 

 The central portion of the spicule is perforated by four holes, placed 

 along the long axes and around the centre of the spicule. On the pro- 

 duced axis of the spicule one, two, or even three additional holes may be 

 developed. In some individuals the holes on the shorter of the long 

 axes are usuallv circular, while those near the centre on the long axis 



