34 C. F. JEXKIX. 



beyond the last tlagellated chamlter. At the juuctiou there are specially large quadri- 

 radiates lying diagoually, apparently strengtheniug the junetiou between the dermal 

 and gastral skeletons. The basjil rays of the chiactines are much longer than the 

 thickness of the body in the upper part of the sponge and project, often half their 

 length, outside the cortex. The regular arrangement of the oscular quadriradiates at 

 the oscular edse is shown in Fig. 111. Side views of these spicules are drawn, 

 showing the diminution in the length of the apical ray. These spicules lie in the 

 middle of the frino^e, so that thev are almost hidden fi-om both inside and outside. In 

 the same figure is shown one of the large quadiiradiates from the junction between 

 tube and bodv. 



There are numerous ova in gome of the specimens. 



Spicules (Fig. 105). 

 O.rea. There are three sorts of Oxea : — 



(a) Large projecting oxea, straight, and pointed at both ends. Largest fragment 



found, 2 "7 mm. long X 14)u. thick. 

 (/() ^linute, .-opined, .slightly crooked, hastate oxea from the dermal layer, 75 yx 



to 85 /n long X 5 /t to 6 yx thick, 

 (e) Rather longer, small, straight hastate oxea, 120 yx to 140 /a long x 4 /x thick. 



The Triradiates are of one sort : — 



(f/) Alate triradiates from the dermal kyer (these are probably the same as 

 those occasionally found in the body-wall). Ba.sal ray straight, tapering to 

 a point, 200 /A to 380 /x long x 8 /x to 10/x thick. Paired rays nearly equal 

 in length, curving slightly upwards, forming a rounded bend at the centre 

 140 /x to 210 /i long X 8/x thick. Oral angle 102° to 106°. There are 

 a very few triradiates with an oral angle of 160°. It is doubtful where 

 these come from. 



{e) Chiactines. Ba.sal ray straight in facial view, but bent slightly in side view, 

 tapering to a sharp point, 400 /t to 600 /x long x '8/x to 10 /a thick. Paired 

 rays about equal, sharply pointed, nearly straight, 160 /x to 200 /x long x 8 /x 

 to 12/x thick. Ural angle 160°. One of the paired rays is sometimes 

 deflected from its usual position into line with the opposite paired ray. 

 (t type of triradiate system.) Apical ray straight, or slightly bent, 

 tapering uniformly to a sharp point, 110/x to 130 /x x 8 fi to 12/x thick. 

 Set-over about equal to the thickness of the ray. Angle between basal 

 ray and apical ray 150° to 155°. 



Osculai' spicules. 



{/) Long, straight slender oxea forming the fringe, 2 • 5 mm. long x 6 /x or less 

 thick, minutely hastate at the outer end. 



