714 PEOP. A. DENDT AND MR. R. W. H. ROW ON 



spicules, with their basal rays centrif ugally directed and their oral 

 rays lying in the deeper part of the gastral cortex. The spicules 

 of the other joints of the tubar skeleton, on the other hand, 

 appear to arise in the walls of the chambers themselves, and this 

 difference in mode of origin probably accounts for the difference 

 which undoubtedly exists between them and the subgastral 

 spicules. 



We consider that the abolition of the families Chiphoridae and 

 Staurorrhaphidse will effect a much needed simplification in the 

 classification of the group, and also that it is highly desirable to 

 do away with them from the point of view of practical con- 

 venience, for to draw a real distinction in practice between a 

 so-called chiactine and an ordinary subgastral sagittal qviadri- 

 radiate is quite impossible. The bending of the apical ray, 

 whereby it is brought to lie neax'ly or quite in the same straight 

 line as the basal ray, is merely a question of degree, as may be 

 seen from the examination of the apical rays of ordinary gastral 

 quadriradiates in various species. 



The family Grantillidpe, proposed by one of us [Row, 1909] 

 has, of course, also been a.bandoned by us. The rejection of 

 Jenkin's chiact theory and the fact that we attach little import- 

 ance to the mere presence of subdermal quadriiadiates, have 

 removed both the characters on which the family was founded, 

 and it has consequently been merged in the Heteropiida?. 



The presence, however, of subgastral sagittal spicules (tri- 

 radiates or quadriradiates) appears to be very characteristic of 

 the Sycettid as contrasted with the Leucascid-Leucaltid line of 

 descent. 



The distribution of oxea in the Calcareous sponges pi'esents an 

 extremely difiicult problem, as species possessing them occur side 

 by side with species that lack them in almost all the large genei^a 

 throughout the gi'oup. As a result we have found it impossible 

 to assign to this character any such important place in our scheme 

 of classification as previous authors have suggested, though as a 

 matter of practical convenience we have used it as a basis for 

 arranging the species of a genus in sections. Certainly the ability 

 of some sponges to produce oxea may be looked upon as differ- 

 entiating them, at any rate to some extent, from others which 

 either have lost this power, altliough descended from oxea-bearing 

 ancestors, or else have never possessed it. 



Further, we have found that two types of oxeote spicules 

 can be distinguished — the comparatively large, usually radially 

 arranged form, and a much smaller for which we employ the term 

 'microxea.' In typical cases the latter are less than 0"1 mm. in 

 length, and they are usually of a- very definite hastate shape, 

 with an enlargement at a short distance from the distal extremity. 

 They thus form very characteristic and well-defined skeletal 

 elements, and it is remarkable to find them recurring in so many 

 perfectly distinct genera, belonging to most of the families within 



