450 DR. J. S. BOWERBANK ON THE SPONGILLID^. [NoV. 24, 



of them are subglobose ; but the most striking specific character 

 exists in the birotulate spicula of these organs, which vary remark- 

 ably in form and proportion from those of any known Indian species 

 of Spongilla. While those of S. Meyeni rarely exceed two diameters 

 of the rotulse in length, in S. plumosa they nearly all range from 

 three to three and a half diameters long. The shaft is equably 

 cylindrical throughout its whole length, and is abundantly furnished 

 with stout spines, frequently exceeding the diameter of the shaft in 

 length. The rotulse also are essentially different from those of either 

 S.Jluviatilis or S. Meyeni : in those species they are thin, flat on 

 both sides, and irregularly and deeply dentate, the divisions reaching 

 very nearly to the centre of the rotulse ; while in this species the ro- 

 tulse are internally concave and considerably and regularly convex on 

 the outer surface, having the circumference only slightly dentate in 

 comparison with the species above named, and, whether in situ after 

 preparation in nitric acid, or in a state of separation, they are per- 

 haps the most beautiful form of spouge-spiculum with which we are 

 acquainted. 



The occurrence of subsphero-stellate spicula in the sarcode of this 

 species is a remarkable fact, as they have not hitherto been found in 

 any species of the genus ; nor are they frequently found among the 

 marine Spongiadee. They occur in the sarcode of Tethea lyncurium, 

 but the radii are acutely terminated and are without spines. In 

 Pachymatisma Johnstonia they abound in the sarcode, with very short 

 incipient spines on the radii ; and in Geodia carinata, from the South 

 Pacific Ocean, Bowerbank MS., I obtained one spiculum in which 

 the rays are profusely spined. In Dactylocalyx pumicea, Stutch- 

 bury, multiradiate spicula are found, the radii of which have either 

 acute or depressed capitulate terminations, but without spines ; and 

 it is only from Spongilla plumosa that I have observed them to have 

 pileate or capitulate terminations and have the radii at the same 

 time strongly spined. The subsphero-stellate spicula are exceedingly 

 variable in the mode of their development : sometimes there is one 

 comparatively large straight fusiform spiculum, pileate at one or both 

 ends, and one or more slightly developed rays dispersed near the 

 middle of it, also more or less pileated ; but the general form is a 

 series of rays of nearly equal length radiating from an irregularly 

 formed common centre, having a few recurved spines on the shaft, 

 and a closely packed cluster of recurved spines at the apex, which 

 take the shape of a little cap closely resembling a young mushroom 

 in form ; but when not fully developed, they assume the appearance 

 of an irregular capitulum. Occasionally, but not very frequently, 

 they terminate acutely. The extreme diameter of a well-developed 

 cluster of radii is about g-i-jj inch. 



These beautiful spicula are not mentioned in the specific descrip- 

 tion of this Sponge by Mr. Carter ; but he subsequently observed 

 them and mentioned them in a letter tome in the latter part of 1854. 



That author in his paper observes, " I have only found three or 

 four specimens of it (S. plumosa), and these only in two tanks. I 

 have never seen it fixed on any body, but always floating on the sur- 



