new Recent Pharetronid Sponges. 513 



and that the scleroblasts may be extremely modified en- 

 veloping telmatoblasts. I have no direct evidence to bring 

 forward in support of this hypothesis, and there is much to 

 say against it, but the investigation of the remarkable cement 

 formation in Lithoninae and Merlin ?e affords, I think, some 

 justification for the statement that a theory of this kind may 

 be worth considering. 



List of Lithoninse and Merlinse. 



Subfam. Lithonin^e, Doderlein. 



1. Petrostroma schuhei Doderlein. Japan, 109-218 fins. (i. p. 15.) 



2. Plectroninia hindei Kirkp. Funafuti, 50 fms. (4. p. 345.) 



A minute specimen provisionally placed in genus Plectroninia, Hinde 

 (3. p. 51.), but doubtfully belonging there. 



3. Minchinella lamellosa Kirkp. New Hebrides, 70 fms. 



Subfam. Merlins. 



4. Merlia normani Kirkp. Porto Santo, 60 fms. 



Index of Literature. 



(1) Doderlein, L. " Ueber die Lithonina," Zool. Jalirb. Bd. x. Syste- 



matik, 1879. 



(2) Hinde, G. J. Catalogue of the Fossil Sponges in the British 



Museum. 1883. 



(4) Kirkpatrick, R. " Description of Sponges from Funafuti," Ann. 



& Mag. Nat. Hist. (7) vi. 1900. 



(5) Lister, J. J. Astrosclera willeyana, the Type of a new Family 



of Sponges. A. WihVy's Zoological Results, part iv. Cambridge 

 University Press, 1900. 



(6) Zittel, K. A. vox. " Studien iiber fossile Spongien," Dritte 



Abth. Abhand. k. b. Akad. Miinchen, Math.-Phys. CI. Bd. xiii. 

 1879. 



(7) . Grundziige der Palaontologie, Abth. i. 1 11 vertebra ta. Ed. 2, 



1903. 



EXPLANATION OF THE PLATES, 



Plate XIII. 



Minchinella lamellosa, gen. et sp. n. 



Fig, 1. Minchinella lamellosa. Specimen A. The type. Poral surface 



Nat. size. 

 Fig. 2. The same ; oscular surface. Nat. size. 

 Fig. 3. Smaller specimen, B ; poral surface. Nat. size. 

 Fig. 4. Pore-chimneys of spec, A, X 3. 

 Fig. 5. Oscular chimneys of spec. A, x 3. 

 Fig. 6. Poral chimneys of spec. B, X 3. 



Fig. 7. Excurrent canals with flagellated chambers (spec. B), x 90, 

 Fig. 8. Collar cells, x 880. 

 Fig. 9. Telmatoblasts (mortar cells), x 880. 

 Fig- 10. Embryo, section, X 121. 



