210 APPENDIX. 



3. STELLETTA LACTEA, Carter. 



Stelletta lactea, Carter. Ann. Nat. Hist., ser. 4, vol. vii (1871), 

 p. 9, pi. iv, figs. 1522. 



Massive, spreading, fixed, following and filling the 

 cavities of deciduous small boring shells (Saxicavce) 

 and Annelids, communicating with the exterior only 

 through the openings of the cavities. Dermal layer 

 thin, white, densely charged with minute stellates. 

 Body-substance opalescent, soft, compact, composed 

 of areolar sarcode traversed in all directions by the 

 branches of the excretory canal systems, which, uniting, 

 finally terminate in their respective oscules, charged 

 more or less with the same kind of stellates as those 

 of the dermal membrane, together with minute sheaf- 

 like bundles of acerate spicules, which in certain 

 directions reflect the light like the micaceous particles 

 in granite. 



Spicules of five kinds. 1. The largest, acerate, 

 smooth, fusiform, slightly curved, about -^th of an 

 inch long ; 2, trifid, smooth, with shaft pointed at one 

 end and provided with three arms at the other, 

 spreading horizontally in the opposite direction, more 

 or less inclined forwards towards the long axis of the 

 shaft, vase-like, straight or slightly flexuous, smooth, 

 pointed. These spicules are ^th of an inch long ; 3, 

 the same, with the ends of the arms more or less 

 bifurcated ; 4, stellate spicules, with long body and 

 short thick rays, or with long rays and hardly any 

 body, about -^o^th of an inch in diameter ; 5, sheaf- 

 like bundles of minute, smooth, acerate spicules lying 

 parallel to each other and about yoVuth of an inch 

 long. The large acerate spicules are more or less 

 spread throughout the sponge, the trifid ones of both 



