PROF. P. M. DUNCAN ON THE GENUS DIRRHOPALUM. 489 



Outer Skeleton. — Large and smaller attenuate- acuates basally 

 spined. 



Sub fusiform acuates with ovoid basal inflations, minutely spi- 

 nulate. 



Body. — Curved, cylindrico-globose-beaded, entirely-spined 

 spicula. 



Derm. — Cylindrical, cylindrical laterally spined, linear cylin- 

 drical minute, and minute fusiform spicula. 



One large bihamate spiculum is amongst a whorl of spicula ; 

 but as it is in company with a coccolith, it is probably a foreign 

 body. 



Description of the Spicula. — Tbe large skeleton-spicula, axial 

 to tbe whorls, few in number, protrude at right angles to the 

 mass of the sponge and extend beyond any of the others, forming 

 a regular series of nearly equidistant sharp projections, glassy in 

 appearance. They are slightly bent, and gradually taper from 

 their rounded base (which is placed amongst the cylindrical 

 curved and bossed spicula of the body) to their apex (which be- 

 comes sharp rather suddenly). The rounded head is minutely 

 and scantily spinulate and is about ¥ \-$ inch in diameter, and 

 the whole spicule is ^ inch long (PL XXIX. figs. 28 & 30). 

 Sometimes very minute spinules exist for some distance up the 

 spicule, which, moreover, has a minute axial canal. Some others 

 (attenuato-acuates), smaller than these, but having the same 

 shape and direction, exist, and they are evidently correspondingly 

 immature spicula. 



The whorled spicula (PI. XXIX. figs. 24-27) are very slender, 

 straight, and have a basal inflation of the ovispinulate type. 

 This oviform enlargement is excessively minutely spinulate, 

 and joins the shaft at a constricted neck. The shaft is fusi- 

 form, but the swelling is in the basal third of the spicule ; thence 

 the spicule becomes slenderer, and ends rather suddenly by be- 

 coming sharp-pointed. In some instances there are a few very 

 minute point-like spines on the shaft near the neck. Some 

 basal inflations are very ovoid, others are more globular ; but in 

 every instance the external or terminal portion is narrower than 

 that just within and nearer the neck. The usual length of these 

 spicula is y^ inch, and the breadth -girwff inch. The swelling 

 of the shaft and the constricted neck and small-spined ovoid 

 base are very distinctive. They are very numerous, and are 

 placed in one or two whorled layers ; the bases are towards the 



LINN. JOUEN. — ZOOLOGY, VOL. XV. 38 



