.Mr. II. .1. ( Jartor nn dm nrw Calcispongla?. 3 



" vtllosaj'^ troni it.-* siirt'aco l)cing somewhat like the ])ili' (»n 

 velvet, a.H a))i)ve statrcl. 



The spicule liappon."* to l)c almost a facsimile of that whifli 

 fomis the tuluTcIrs ami niist on the hack of Don's txihercnlnta, 

 and, like it as well as all the other calcareous spicules that I 

 have met with in the Calcispon^iie, Foraminifera, (iorgo- 

 nii(la% Echinoilcrmata, and comijound tunicated animals, pre- 

 sents no central canal, but is solid throughout. 



Leuconia Johnstonii\ luihi. 



ri. I. hgs. 5-12. 



Massive, Hat, sessile, lobulated, snow-white, each li>l»ule 

 having a single vent situated at the end of a more or less 

 elongated, conical or rounded eminence (PI. I. fig. 6). Sur- 

 face smooth, covered with very large quackiradiatc spicules 

 (fig. G, r). Vent circular, and surmounted by a crown of erect 

 linear spicules {i\<^. it, a and 7, e), or simple and bound down 

 marginately by the spreading amis of the great quadriradiate 

 spicules of the surface (fig. 6, l>, and fig. 40, i /> A, IM, 11.), 

 leading into a cloacal cavity (fig. 7, a) which soon branches oflf 

 into the excretory' canal-system (fig. 7,h b). Pores scattered irre- 

 gularly over the surface, in the dermal sarcode, chiefiy opposite 

 the interstices of the intercrossing subjacent spicular structure 

 (fig. 9, f7, b). Intenially areolar for the most ])art, accompanied 

 by the branching excretory canal-system (fig. 7,^/ ddd) ; areolar 

 cavities opening into each other (8, n) and finally intu the cloaca 

 directly (fig. 7, c c) or indirectly into it through the branches of 

 the excretory canal-system. Spicules of seven forms : — 1, the 

 largest, quadriradiate (fig. 10, a), one arm of which is directed 

 internally (r), while the three others {b b & d), lying flat upon 

 the surface (fig. 6, r), thus, nail-like, bind down the spicular struc- 

 ture ; internal arm (r) much curved, ])rojecting into the cloacal 

 cavity, where it presents a formidaljle spur bent towards the 

 vent (fig. 7,f) ; the junction of the radii marked by a transpa- 

 rent area, which is white or dark according to the direction of 

 the light, and arises from the presence or junction of the in- 

 ternal or fourth arm, Avhercby this part often has the appear- 

 ance of a pore (fig. 12) ; 2, triradiate {j), very much smaller 

 than the last, but of different sizes, and forming, as in most 

 calcareous sponges, the staple spicule of the mass ; 3, thick, 

 long, linear, smooth, insequifusiform, slightly curved, larger at 

 the proximal than at the distal end (e) ; 4, long, delicate, 

 hair-like, straight (/) ; the last two are confined to the vent 

 (fig. 7 <?) ; 5, small quadriradiate (it'), with one arm straight and 

 long, two short and opposite or lateral, and the fourth forming 

 a long curved spur directed forwards, which, as this spicule is 



1* 



