114 EOYAL SOCIETY OF CANADA 



Suborder Monactinellida, or of doubtful affinity. 

 Genus LASIOTHEIX, Hinde.' 



Sponges small, depressed oval in outline, the outer surface covered 

 by a layer of longitudinally arranged, apparently simple, acerate spicules ; 

 beneath this is another layer of s))icules disposed transversely. From 

 the base of the sponge several simple elongated spicules extend. 



The peculiar arrangement of the surface spicules in this form indi- 

 cates a probably new genus, but in its present ccmdition one cannot tell 

 with certainty whether it is monactinellid or hexactinellid. The outer 

 surface seems to have been invested with a sheathing of regularh ar- 

 ranged acerate spicules, and beneath these other spicules, disposed trans- 

 versely, can be distinguished, but wliether these are really acerate or 

 moditied hexactinellid spicules there is no decisive evidence to show. 

 In one or two instances the spicules appear to be cruciform, and the 

 presence of the long, simple anchoring-spi extending from the base 



of the sponge, precisely as in normal hexa^ allids, is a further point in 

 favour of its belonging to this division. 



11. — Lasiothrix curvicostata, Hinde. 



(Fig. 24.) 



The type form is transvei-sely oval, 8 mm. in height by 12 mm. in 

 width, the anchoring-spicules can be traced to a length of 15 mm. from 

 the body. The summit is rounded. Thei-e are some nodular elevations 

 of P3']"ite8 in the body portion, but it is doubtful whether they represent 



Fig. 24. — Lasiothrix curvicostata. Natural 

 size and portion enlarged. 



aggregations of spicules or are merely due to the chemical deposition of 

 the mineral, in connection with the presence of organic matter. 



This curious little sponge, of which few specimens were found, is 

 remarkable for the strong cui'voil spicules which sup])ort its sides, giving 



1 British Fos.sil Sponges, Pal. Soc, 1888, PI. i., fig. 3. 



