CALCAREA. 33 



bluntly pointed, 220 /t to 260 /i long, x 12/i to 14 ft thick. Oral angle 

 130 to 160. 



(</) Chiactines. Basal rays straight, tapering to a more or leas sharp point, 

 450/i to 550 /t long x 12 ft to 16 /i thick. Paired rays equal, straight, 

 240/i to 270/i long x 12/i to 14/i thick. Oral angle, 155 to 160. 

 Apical ray sharply pointed, maximum length IGO/i long x 14/i to 16 /i 

 thick. Angle between apical ray and basal ray, 165 to 180. 

 Oscular gpiculcs. 



(e) Quadriradiates from the oscular tube. Basal rays straight, tapering 

 uniformly to a sharp point, 650 /i long x 12/i thick. Paired rays often 

 unequal, maximum size 560 /i long x 14 /i thick, nearly parallel, bluntly 

 pointed. Oral angle about 160. Apical ray sharply pointed, curved 

 orally, 1 20 /i long x 9 /i thick. 



* 



ACHRAMORPHA NIVALIS. 



(Plate XXVII., Figs. 7 and 8. Plates XXXV. and XXJCVI., Figa 105-112.) 



There are fourteen specimens of this new species in the collection. They vary 

 considerably in shape, but are mostly more or less pear-shaped, with the oscule at the 

 narrow end (see Figs. 7 and 8). In some specimens the neck of the pear is considerably 

 extended, but the actual oscular collar (without flagellated chambers) is always quite 

 short There is a dense fringe of long shining silver-white hair spicules round the 

 oscule, which sometimes attain a length of 2*5 mm. The whole sponge is covered 

 with long projecting oxea which lie in all directions, giving it a very untidy appear- 

 ance. The base of the sponge is rounded. 



The dimensions of the perfect specimens are as follows : 12 mm. x 3 mm. 

 17 mm. x 3 mm. ; 18 mm. x 9 mm. ; 20 mm. x 8 mm. ; 12 mm. x 4 mm. ; 8 mm. 

 X 4 ram. ; 11 mm. x 5 mm. ; 17 mm. x 8 mm. ; 8 mm. x 2 mm. ; 26 mm. x 

 12 inia. ; 29 mm. x 10 mm. 



The structure of the body-wall is shown in Fig. 106, where the subdermal 

 cavities and exhalent chambers may be seen. The small projecting oxea are mostly 

 arranged round and over the ostia. This may be seen in Figs. 107 and 108 repre- 

 senting the dermal cortex in plan and section. The very large projecting oxea are 

 scattered quite irregularly, and often project through the body-wall into the gastral 

 cavity. The large oxea are all broken ; the longest fragment found is 2 7 mm. long. 

 They lie at all angles. Fig. 109 represents the gastral membrane as seen from inside. 



Figs. Ill and 112 represent the oscular structure. The highest flagellated 

 chambers are shown in Fig. 112, and the short oscular collar projecting about 

 1*3 i ii in. beyond them. Fig. 112 shows the junction of the oscular tube and 

 the body to a larger scale. Above the last chamber the skeleton consists of quadri- 

 radiates and oxea only ; the triradiates forming the dermal skeleton do not extend 



2 M 2 



