232 ART. 7.— I. IJIMA : IIEXACTINELLIDA, IV. 



oxyhexactins may have rays 95 t^- long and 8 n thick at base, the 

 entire surface being thinly microtubercled. Their position and 

 manner of occurrence scarcely warranted interpreting them as 

 gastralia. 



The derraalia are both stauractins and pentactins in about 

 equal numbers (Contrib. III., PL IIL, fig. 1). Size various, 43- 

 152/^ m length of rays and 4-9/^ in breadth at their base. The 

 relatively strong and slightly tapering rays are entirely rough on 

 account of sparse but distinct microtubercles. Tlie atrophied rays 

 are sometimes represented hj an external and an internal knob 

 in the stauractins, and by an external knob in the pentactins. 

 The larger dermal pentactins approach in size the pentactinic 

 hypodermalia in which the paratangential rays may reach 380 1^ 

 in length and are smooth except near the ends. 



The gastralia are hexactins found in scattered distribution 

 {I. c, PI. IIL, fig. 2). Rays as in dermalia ; length, 34-72 IK 



Oxyhexasters (/. c, PI. Ill,, figs. 3 and 4) are of common 

 occurrence. They are normally developed, there being two or 

 three, slender and rough-surfaced terminals to each principal, 

 which is short. Diameter, 88-1 OG //. 



Discoctasters (/. c, PI. IIL, fig. G), a small number found ; 

 small and si ender- ra yed ; measuring 130-144 /< in diameter. 



Microdiscohexasters (/. c, PI. IIL, fig. ö), very small and 

 delicate; 15,« in diameter. They occur in abundance in the wall, 

 l)ut especially in the periphery. 



The basidictyonal mass is of the usual structure, l^eing com- 

 posed of fused hexactins with thick, short and sparsely micro- 

 tubercled rays. The skeletal beams of the Hexactinella, at the 

 spot giving attachment to the specimen, are entirely enveloped 

 by a thin and small-meshed limiting plate. 



