CRATEROMORPHA PACHYACTIXA. 77 



The ankylosis of certain spicules in the lower ])art of the 

 stalk occurs in much the same manner as in (J. meyeri. Per- 

 haps it may Ije regarded as a point of slight difference that the 

 obsolete microtubercles on the beams of the basal framework are 

 comparatively sparsely |»resent in an irregular distribution. 



Btrongly developed as are the j^arencliymal piincipalia, a far 

 more striking feature is olfered by the unusually thick-rayed 

 hypodermal o.vypentaotins (PL IV., fig. lo). These occur in 

 abundance on both the body and the stalk. Handling the sponge 

 without due care is liable to lead to the irritating result of find- 

 ing them impertinently sticking to the skin by their sharp 

 points. 



While some of the pentactins — evidently those not yet fully 

 developed — have indeed comparatively slender rays, most of them 

 have rays so thick that they may be said to l)e nearly of an 

 elongate conical shape. Wath a length of 24 mm. (as measured 

 from the spicular center), the rays may be 330 // thick close to 

 their base. They taper gradually towards the sharply pointed 

 ends and are smooth throughout. All the rays in one and the 

 same pentactin are of nearly equal lengtli. The plane of the 

 paratangentials is usually convex on the outside. The pentactins 

 in situ can be discerned witli the naked eye and picked up one 

 by one by means of a pincette. In PI. IV., fig. 13, a few der- 

 malia and some fine parenchymalia (comitalia) are drawn by the 

 side of a hypodermal pentactin in order to show at once the 

 striking difference in bulk. 



No other spicular forms than the above pentactins can be 

 distinguished as hypodermalia. The dermal layer lies in most 

 places in direct apposition to the parenchymal mass, and there- 



