CALCAREA. 31 



ArHKAMuKI'HA CI.ACIAUS. 



(I'liitt- XXXIV., Figs. 98-102.) 



There are six specimens of this new species in the collection. All are small, 

 slender, vase-shaped Sponges, which when examined with the naked eye might easilv 

 lie mistaken for Ascons. In colour they arc white tinged with orange, as preserved in 

 alcohol. The dimensions of the four perfect specimens are as follows : 9 mm. x 2 nun. : 

 4 mm. x '75 mm. ; 8 mm. x 1'5 mm. (flattened) ; 9 mm. x 1^ mm. 



The structure of the body wall is shown in Fig. 101. The flagellated chambers 

 often taper considerably at their distal ends, thus leaving rather large inhalcnt 

 chambers under the dermal cortex. The hair oxea lie in the very thin mesodcrm 

 between the chambers and project beyond the dermal cortex. Neither they nor the 

 large projecting oxea are arranged in regular tufts or cones, but appear to be 

 irregularly scattered. 



The structure of the oscule is shown in Figs. 100 and 102. The section shows 

 the transition from normal to centrifugal position of the quadriradiates. It also 

 shows the diaphragm. 



Fig. 98 represents a view of the gastral layer. The section includes some of 

 the gastral ports and some of the apopyles which lie immediately above the ports. 

 There are a very few minute oxea lying radially in the gastral layer. One of these is 

 shown in Fig. 102. In some specimens these minute oxea are scattered throughout 

 the body wall. Several of the specimens contain ova of the usual form. 



Spicules (Fig. 99). 

 Oxea. The Oxea are of three sorts : 



(a) Stout projecting oxea, irregularly bent, sharply pointed at the inner end, 

 and bluntly pointed at the outer end, 280 /* to 440;* long x 12 /t to 24 /j. 

 thick. 



(li) Minute, hastate, slightly bent oxea, some smooth, some spined, from the 

 dermal layer, 35 /* to 40 /* long x 2 /t to 3 p, thick. 



(c) Hair oxea, 400 /* or more long. 



The Triradiates are of one sort : 



(<l) Alate triradiutes from the dermal cortex. Basal rays straight, tapering and 

 sharply pointed, 200 p. to 380 p. long x l~2 p. thick. Paired rays equal, 

 nearly straight, 130 p, to 180 p. long x 10/n to 14 p. thick. Oral angle 

 varying widely, 110 to 160. Folding very variable. 



(<') C/i/cfhi<'.. Basal ray straight, tapering, sharply pointed. :!40/z t<> 400 p. 

 lung x 15 /A thick. Paired rays equal, 130 p. to 180 p. long x 16 p. thick, 

 bent slightly irregularly. Oral angle, 145 to 165. Angle of fold, 150 



VOL. IV, 2 M 



