40 Mr. H. J. Carter on 



surface and holes of the cloaca thickly echinated with the 

 fourth arm of quadriradiates curved towards the mouth. 

 Structure of the wall consisting of radial chambers, most evi- 

 dent on the cloacal side, where they are defined by the long 

 shafts of triradiates, whose heads are against the cloaca and 

 whose shafts, directed perpendicularly outwards, abut upon 

 the cortex, which consists of several layers of tolerably hrge 

 triradiates, and is thus very thick ; chambers uniformlj' 

 pierced by pores alone until arriving at the cortex, where 

 their continuity is broken up by the presence of large holes of 

 intercommunication, which are continued to the pore-areas of 

 the surface through a similar structure in the midst of the 

 cortex. Spicules of three kinds, viz. acerate, triradiate, and 

 quadriradiate : — 1, acerates, of two forms, viz. that common 

 to the peristome in general and that of the surface, the latter 

 minute and sinuous, with one end enlarged and lanceolate, in 

 short the " mortar-spicule," about 28 by l-6000th in. ; 2, tri- 

 radiates, also of two forms, both large, viz. those which com- 

 pose the cortex, which are more or less regular, and those 

 whose long shafts define the radial portion of the chambers, 

 where they average 115 by 12-(i000ths ; 3, quadriradiates, 

 with large, ensiform, curved fourth arras. No. 1 is confined 

 to the peristome and surface ; no. 2 to the cortex and interior 

 of the wall, where the heads of the " long shafts " rest against 

 the cloaca ; no. 3 to the surface of the cloaca, where the fourth 

 arm, which is stout, ensiform, and curved towards the mouth, 

 profusely echinates the whole surface. Size of specimen 

 about 6-12ths in. long by 2-12ths in. in its greatest transverse 

 diameter. 



Ohs. The structure of this specimen so gave way that it 

 became crushed under the knife while making the section j thus 

 the wall and cloaca together became separated from the 

 cortex. This in part might have been occasioned by de- 

 composition, as indicated by the ferruginous colour of the 

 inner portion ; but it may be here stated that it is very likely 

 to occur where the spicules are large and thick, on account of 

 the little resistance then afforded by the sarcode ; hence the 

 advantage to be gained by imbedding the portion in paraffine, 

 when the spicules are so tirmly kept in their natural position 

 that during the section they cannot swerve from it. There is 

 enough present, however, in my section to show that there is 

 still a portion of the typical radial chamber left in this species, 

 and that it is " inarticulate ; " while the thickness of the cortex, 

 exceeding that of any other specimen in the collection, is very 

 remarkable. 



