298 



ERYLUS ROTUNDUS. 



11-13, 16b) are more numerous than the sharp-pointed amphioxes. Some 

 of the amphioxes, this was particularly observed in form B of var. typica, appear 

 as amphistrongyles, the blunt ends of which are surmounted by small conical 

 tips. These tips may be simple or terraced, telescope-like. Angularly bent or 

 branched rhabd-derivates have chiefly been observed in form A of var. mega- 

 rhahda and in var. cidaris. The spicules of this kind in the last-named variety 

 appear as transitional forms connecting its aster-like rhabd-clusters with the 

 ordinary rhabds. 



The dimensions of the rhabd megascleres and the relative frequency of the 

 sharp-pointed and blunt amphioxes and amphistrongyles in the different forms 

 and varieties are tabulated below. 



Rliabd megascleres 



Erylus ro fundus 



var. megarhabda 



var. typica 



var. 

 cidaris 



limits and means of averages of 

 all the forms of the species 



A 



B 



limits and means of averages of 

 all the forms of the variety 



A 



B 



C 



D 



limits and means of averages of 

 all the forms of the variety 



South Moloka'i 



Kauai 



South Molokai 



Kauai, dark specimen 



Kauai, light specimen 



Nortlieast Hawaii 



Length 



limits, p 



330- 

 650 



350- 

 550 



330- 

 650 



320 

 570 



330- 

 560 



350- 

 520 



310- 

 490 



310- 

 570 



440- 

 650 



310- 

 650 



average of the 

 longest three, /( 



603 



543 



573 



556 



533 



507 



477 



518.3 



617 



548 



Thickness 



limits, fi 



6-13 



6-12 



6-13 



6-11 



6-12 



6-11 



7-15 



6-15 



8-12 



6-15 



average of tlie 

 thickest tiiree, /( 



13 



11 



12 



11 



11 



11 



14 



11.3 



12 



11.9 



Shape 



mostly sharp-pointed amphioxes; blunt 

 forms rare. 



mostly sharp-pointed amphioxes; blunt 

 forms rare. 



mostly sharp-pointed amphioxes; blunt 

 forms rare. 



mostly amphistrongyles or blunt am- 

 phioxes ; sharp forms rare. 



sharp-pointed and blunt amphioxes 

 and amphistrongyles; the first named 

 most nuinerous. 



mostly sharp-pointed amphioxes; blunt 

 forms rare. 



mostly amphistrongyles or blunt am- 

 phioxes; sharp forms rare. 



amphistrongyles, blunt and sharp-point- 

 ed amphioxes; in some the blunt in 

 others the sharp forms preponderate. 



mostly sharp-pointed amphioxes; blunt 

 forms rare. 



sharp-pointed amphioxes; blunt am- 

 phioxes; amphistrongyles; variously 

 combined. 



