24 R. KIRKPATRICK. 



FAMILY DESMACIDONID^E, Ridley and Dendy. 



I. SUB-FAMILY ECTYONIN^;, Kidley and Dcndy. 



HYMEDESMIA AREOLATA. 



(Plate XXII. , fig. 3-3c.) 



1905. Hymedesmia areolata Thiele (23. p. 452). 



There are two specimens, one a fine large one, the other a small nodule ; both have 

 a broken surface, and on the label is the legend " Broken off a stone." 



The larger specimen is an oval mass 12 '5 cm. long, 6' 5 cm. high, and 5 '5 cm. 

 thick. 



The species is easily recognised from the areolated appearance of the surface. 

 There are numerous oval or circular poral pits, 1 5 mm. across, with over-hanging 

 edges ; the concave floor is perforated with pores. 



The densely packed ectosomal oxeas are arranged radially round the pore pits. 



The oscules are small inconspicuous cones contracted to a point. 



The flagellated chambers are aphodal, 36 X 23 /x in diameter. 



Thiele's specimens were in the form of incrustations on chitinous tubes. 



The ' Discovery ' specimens were dredged near Winter Quarters in 12f fms. 



The species has also been recorded from Calbuco, Chile, 40 metres (Thiele). 



HYMEDESMIA EXIGUA. 



(Plate XXII., fig. 4, and Plate XXVL, figs. 2a-f.) 

 1907. Hymedesmia exigua Kirkpatrick (10a. p. 273). 



Description. The sponge forms a thin translucent grayish-white crust, about 

 5 mm. in diameter, on a stone. The surface is smooth, and the substance of a fleshy 

 consistence. 



The skeleton. The choanosome contains scattered short acanthostyles, and the 

 dermal membrane tangential tylotes isolated or in bundles of a few. 



Spicules. Megascleres. Acanthostyles, 94 x 19 /i, short, thick, with spines 

 pointing backwards slightly. Ectosomal tyles, 157 X 3'5 //,, straight, smooth, with 

 oval heads, 5 /u, long, and 4 ' 5 fi broad. 



Microscleres. Pluridentate isancorae spatuliferae : with five foliate teeth, 5 /t in 

 length, at each end, sometimes with three or four ; shaft deeply curved, 2 5 fi thick, 

 sometimes with central alate expansions. 



Sigmata 9 ' 6 /t long, 5 6 broad, 5 p thick, scattered separately in the choanosome. 



The new species resembles in several respects H. zetlandica Bowerbank, but the 

 ancorae of the latter have only three teeth, the sigmata are much longer (51 yu) and 

 in sheaves; also the ectosomal tyles are much larger, viz., 328 x 3 '25 /x, and 

 the spines of the acanthostyles more verticillate. Hymedesmia irritans Thiele, from 



