740 PROF, A. BENDY AND MK. R, W. H. ROW ON 



Lelapia difters widely in other chai-acters also from both Min- 

 chinella and Murrayona, Ave are forced to the conclusion that the 

 so-called Pharetronid sponges are at least diphyletic in origin, 

 and we have removed the Lelapiida? to a position in the Sycettid 

 line of descent. We shall, however, discuss the question further 

 under the head of phylogeny. 



The genera Minchinella, Petrostroma and Plectro7iinia all 

 agree in the possession of a stony skeleton composed of fused 

 quadriradiates, and thus differ widely from Murrayona. We 

 therefore unite them in one family under the name Minchinellidae, 

 while relegating Murrayona to a special family of its own. 



Genus 11. Minchinella Kirkpatrick [1908]. 



Diagnosis. Sponge lamellar, with pore-bearing chimneys on one 

 side and oscular chimneys on the other. The quadriradiates 

 of the main skeleton cemented together . into a compact 

 network and completely embedded in the enveloping cement. 

 Dermal skeleton of radiates, including tuning-fork spicules, 

 and oxea. 



For illustrations of this genus see Kirkpatrick [1908]. 



The only known species of the genus is : — 



1. M. lamellosa Kirkpatrick. 



Minchinella lamellosa Kirkpatrick [1908]. 



Genus 12. Petrostroma Doderlein [1892], 



Diagnosis. The quadriradiates of the skeleton of the chamber- 

 layer fused together laterally by calcareous cement into a 

 network. Dermal skeleton of separate quadriradiates and 

 triradiates and bunches of tuning-fork spicules. 



For illustrations of this genus see Doderlein [1897]. 



The only known recent species of this genus is : — 



1. P. schulzei Doderlein. 



Petrostroma schulzei Doderlein [1892]. 



Genus 13. Plectroninia Hinde [1900]. 



Diagnosis. Quadriradiates of the main skeleton with their facial 

 rays truncated or expanded terminally and fused end to end 

 with the facial rays of adjacent spicules, while the apical 

 rays remain free and pointed. Dermal skeleton of separate 

 radiates, including tuning-fork spicules, and oxea. 



For illustrations of this genus see Kirkpatrick [1900 B], 



