Mr. H. J. Carter on two new Calcispongige. 3 



" villosa^'' from its surface being somewhat like the pile on 

 velvet, as above stated. 



The spicule happens to be almost a facsimile of that which 

 forms the tubercles and crust on the back of Doris tuherculata, 

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

 have met with in the Calcispongige, Foraminifera, Gorgo- 

 niidfe, Echinodermata, and compound tunicated animals, pre- 

 sents no central canal, but is solid throughout. 



Leucoma Johnstoniij mihi. 

 PL I. figs. 5-12. 



Massive, flat, sessile, lobulated, snow-white, each lobule 

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

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

 face smooth, covered with very large quadriradiate spicules 

 (fig. 6, c). Vent circular, and surmounted by a crown of erect 

 linear spicules (fig. 6, a and 7, e), or simple and bound down 

 marginately by the spreading arms of the great quadriradiate 

 spicules of the surface (fig. 6, 5, and fig. 40, hhh^ PL II.), 

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

 into the excretory canal-system (fig. 7,bb). Pores scattered irre- 

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

 the interstices of the intercrossing subjacent spicular structm-e 

 (fig. 9, a, b) . Internally areolar for the most part, accompanied 

 by the branching excretory canal-system (fig. 7,dddd)- areolar 

 cavities opening into each other (8, a) and finally into 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 (c), while the three others {bb &d), lying flat upon 

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

 ture ; internal arm (c) much curved, projecting into the cloacal 

 cavity, where it presents a formidable 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, whereby this part often has the appear- 

 ance of a pore (fig. 12) ; 2, triradiate (^), 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 e) ; 5, small quadriradiate {ii'), 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* 



