526 



REVISION OF THE AXINELLID.E, 11., 



Spicules. —The megascleres are slightly curved, subcylindrical 

 to subconical styli, fewer oxea, and scarce strongyla, the three 

 forms differing in general only with respect to the character of 

 their extremities, and connected with one another by numerous 



intermediates. They are often irreau- 

 larly ended and more or less blunt- 

 pointed, and man)' of the oxea are 

 markedly anisoactinate. Their size is 

 very variable both as regards length 

 and stoutness. In the P.P. speci- 

 mens, they range in length from 120 

 or 130 to 360/x in some cases, up to 

 over 400/x (rarely to 450/x) in others, 

 and vary in diameter, irrespective of 

 length, from 2 to 7 or (rarely) to 10//. 

 In the P.J. specimens, they are gener- 

 ally much stouter, attaining a max- 

 imum diameter of from 15 to 17/x, 

 and range in length from about lf)0 to 

 420/i. The styli are, on the average, 

 stouter than the oxea, and the stout- 

 est spicules are mostly those of inter- 

 mediate and lesser lengths. In the 

 case of the P.P. specimens, the 

 shortest spicules, ^ — those of lesser 

 length than, sa}', 200//, — are chiefly oxea, generally with abruptly, 

 often mucronately pointed ends; but, in the P.J. specimens, the 

 shortest spicules are nearly always styli. 



(ii.) The sigmata are extremely slender, — invariably less than 

 1/i.in diameter,— and of two kinds, the smaller (and less numer- 

 ous) varying in length from 9 to 16/x, the larger from 25 to 45//, 

 measured from bend to bend. Both kinds are mostly more or 

 less contort, - the smaller, however, usually onl}?^ slightly so, the 

 larger often to such an extent as to appear S-shaped; both kiiifls 



Text-fig. 12. 



* Sigma.rine/fa avMrariana. a, megascleres; b. c, larger and smaller 

 sigmata. 



