CALCAREA. 



This classification is based primarily on the arrangement of the spicules, as is 

 shown in the following diagram, where the families are arranged in four columns to 

 show their dependence on the spiculation. The families on the same horizontal line 

 correspond more or less in their canal systems. 



NEW FAMILIES. The two new families, Cltij>h<>ri<lre* and Staurorrhaphidsefi axs 

 introduced to contain the 9 new species and 2 old ones which have cliiactine spicules. 

 The name chiactine\ is introduced to denote a special type of quadriradiate spicule 

 which differs from the ordinary quadriradiates both in shape and in position in the 

 sponge. The chiactine is a quadriradiate spiculc lying with its basal ray directed 

 radially outwards (centrifugally) and its apical ray, which is bent at its base so as 

 to lie almost in line with the basal ray, directed radially inwards (centripetally) 

 and projecting into the gastral cavity. This type of spicule has hitherto been 

 found in only 2 species of sponge, each represented by a single specimen, mz., 

 Leucoma crucifera, Pole'jaeff (4) and Grantiopsis cylindrical, Dcndy (7). The 

 former is now included in the new genus M<'I/<I/H></<>II. The latter is transferred 

 to the new family Staworrliaphidse, tlie generic name being retained. In order to 

 make the present report a complete record of all species in the two new families, 

 brief descriptions of Megapogon crucifcm and Grantiopsis cylindrica, with drawings 

 of the spicules, are included. 



In some of the new species this type of spicule occurs in conjunction with the 

 ordinary types, but in several it forms the whole gastral and body-wall skeleton, to 

 the exclusion of the ordinary quadriradiates and triradiates ; its importance, therefore, 

 can hardly be over-rated, and fully justifies the formation of the new 1 families. All 

 the species containing chiactines might have been included in one family instead 

 of two, but as they fall into two groups, which differ from cadi other in the same 

 way that the ,S'//<v///W,r do from the ( !ntiitin1n\ it seemed better to divide them 

 under two corresponding new families. 



i, a cross ; <f>opetv, to bear. 

 'i a cross ; OKI-IS, a ray. 



t (rravpos, a cross ; {K>(J>!S, a needle or spiculc. 

 For a detailed description of the chiactines see Part III. 



