■ CALCAREOUS SPONGES. 739 



already indicated, we no longer consider the presence of sub- 

 dermal quadriradiates, taken by itself, to be a character of generic 

 importance, being convinced that the addition of an apical ray 

 to a triradiate spicule may take place whenever and wherever it 

 may be required. 



It will have been noticed that our genus Leucettusa is identical 

 in scope with Polejaeff's Leucetta [1883], but as we have found it 

 necessary to retain Haeckel's name Leucetta for another genus, 

 as previously explained, we have been obliged to adopt his 

 subgeneric name for the group of species which Polejaeff quite 

 rightly separated out. 



"We recognise the following s]3ecies as belonging to this genus: — 



Section A. "Without oxea. 



1. L. COKTICATA Haechel. Type species of the genus. 



Leucetta corticata Haeckel [1872]. 



2. L. HAECKELiANA PoUjaeff. 



Leucetta haeckeliana Polejaeff [1883]. 



3. L. imperfecta Polejaeff. 



Leucetta imfjerfecta Polejaeff [1883]. 



4. L. SAMBUCUS Preiwisch. 



Leucetta samhucus Preiwisch [1904]. 



5. L. vera Polejaeff". 



Leucetta vera Polejaeff [1883]. 



Section B. With microxea but Avithout large oxea. 



6. L. DICTYOGASTER RoW. 



Leucettusa dictyogaster Row [1913 MS 



Family 4. MINCHINELLID^ nov. 



Lithonina Doderlein [1892]. 

 Lithoninoi Kirkpatrick [1911 A]. 



Diagnosis. Canal system leuconoid (in all known forms and 

 presumably always so). Main skeleton composed of quadri- 

 radiates cemented together in various ways by calcareous 

 cement. Apparently without subgastral sagittal radiates. 

 Nuclei of collared cells (probably always) basal. 



"We have been able, owing to the kindness of Mr. Kirkpatrick, 

 to examine preparations of Minchinella and Murrayona, in which 

 the collared cells are sufficiently well preserved to enable us to 

 determine the position of the nucleus. We find that this is basal 

 in both cases, whereas in Lelapia we find it to be apical. As 



Proc. Zool. See— 1913 No XLIX 49 



