284 



ERYLUS SOLLASII. 



lines extend towards the margin. In some adult asj^idasters this radial structure 

 is well defined (Plate 2, fig. 7), in others it can hardly be made out. 



There appears to be a certain degree of correlation between the size of the 

 sponge and the size of its aspidasters, the latter being smaller in the small speci- 

 mens of race I, forms A and B (average length of the three largest of these forms 

 118 and 120 p. respectively), larger in the middle-sized specimen, race I, form D 

 (that average 124 and still larger in the large specimens of race I, form C, 

 and races II and III. Among the latter those of races II and III (that average 

 150 and 152 /i) are very considerably larger than those of race I, form C (that 

 average 128 /t), and the other smaller forms of race I. Also in their shape the 

 aspidasters of the different forms differ to a certain extent, those of race II 

 being much more slender and those of race I, form C (Plate 2, fig. 25) much more 

 irregular than those of the others. Also in the number of the ray-spines differ- 

 ences are observed, the rays of the aspidasters of race II bearing up to ten, those 

 of the aspidasters of the races I and III only from four to six lateral spines. 



DIMENSIONS OF THE ASPIDASTERS. 



• 



Race 



all forms 



I 



Forms 



11 



III 



A 



B 



C 



D 



limits 



general aver- 

 age of tlie 

 three largest 



general 

 average 



Length 



of all measured, /( 



102- 

 121 



95- 

 120 



105- 

 130 



107- 

 126 



120- 

 1.56 



128- 

 153 



95- 

 156 







average of the 

 three longest, // 



120 



118 



128 



124 



152 



150 





132 





Breadth 



of all measured, /( 



57- 

 68 



55- 

 70 



59- 

 73 



60- 

 75 



60- 

 76 



71- 

 82 



55- 

 82 







average of the 

 three broadest, /i 



67 



69 



73 



73 



75 



82 





73 





Thickness 



of all measured, /( 



7.4- 

 12.2 



8.2- 

 10.4 



10 



11.2- 

 12 



9.2- 

 11.4 



12-14 



7.4- 

 14 







average of the 

 three thickest, /< 



11.6 



10 



10 



11.6 



11 



14 





11.6 





Average of proportion of 

 length to breadth to thick- 

 ness, /( 



100: 

 55.3: 

 8.2 



100: 

 59.1: 

 9 



100: 

 57: 

 8.4 



100: 

 56: 

 9.8 



100: 

 49.8: 

 7.6 



100: 

 57.7: 

 10 







100: 

 55.8: 

 8.8 



