ACANTHASCUS ALANI. IGl 



actins met with here and there in preparations of the septa are 

 either canalaria or gastralia. 



Hypodermalia quite like the above. 



DerriiaUa (Ph X., fig. 16), ahiiost always pentactins ; nsnally 

 with a gentle prominence representing the distal sixth ray. Rays, 

 slightly attenuated outwards but with rounded tip ; microtubercles, 

 not numerous, nor strongly developed, so that the roughness of 

 surface is not pronounced. Axial length, generally 250-350 ,«. 

 Breadth of rays at base, 9-11 !'-. 



Gastralia (PL X., fig. 18), hexactins ; irregularly scattered. 

 Rays, like those of dermalia but with less roughness of surface. 

 Axial length, 280-460 /^. Hexactins similar to the gastralia occur 

 along the excurrent canals as canalaria. In the incurrent canals 

 pentactins resembling dermalia were occasionally found ; they are 

 probably to be considered likewise as canalaria. 



Oxyhexaster, present in abundance. Diameter, 144-190,«; 

 on an average 160/^. From the characters of its rays, two varieties 

 can be distinguished ; both seem to occur together promiscuously. 



In the one variety (PI. X., fig. 20) the center is swollen to 

 a globular node, while the short principals are rounded in a 

 knob-like manner. Slender rough terminals, generally 3 or 4, 

 arise from each principal. They seem to be very liable to be 

 broken off near the base, the fragments being found in abundance 

 in the soft parts. It seems that this is the more abundant of 

 the two oxyhexaster varieties. 



In the other variety (PI. X., fig. 21) the terminals are 

 considerably stronger while the principals are much less distinctly 



