H. B. Kirk. — On Neio Zealand Sponges. 291 



same length as the basal ray, or slightly shorter, curve towards 

 the apical ray ; or one may curve towards the apical and 

 one towards the basal ray. The apical ray is comparatively 

 long, 005mm. ; it is generally slightly curved, and sharply 

 pointed. Between these small dagger-shaped spicules and 

 the large 3-radiates of the oscular region all stages in form 

 and size may be found. 



A peculiarity of this sponge is that the gastral cavity 

 becomes almost entirely obliterated in adult specimens, 

 the exhalent canals converging to open very near the os- 

 cule. In young specimens the gastral cavity is very well 

 marked. 



I am indebted to Dr. Deudy for pointing out clearly what 

 I had, for my own part, only very indistinctly felt — that the 

 parenchymal oxea of this sponge, so like in form to the 

 " mortar spicules " of many calcareous sponges, are probably 

 incursive from the dermal cortex, and replace original paren- 

 chymal radiates, just as in Anamixilla, Pol., the large 

 parenchymal radiates are probably incursive. If this view is 

 correct, Lamontia is especially interesting as showing how 

 the characteristic skeleton of Leucyssa may have been derived 

 from that of Leucandra. 



Locality. — Cook Strait. The sponge is rare. 



EXPLANATION OP PLATES XXIV.-XXVI. 

 Plate XXIV. 

 Sycon dendyi. 



Pig. 1. A group of individuals, natural size. 



Pig. 2. Portion of dermal surface : c, distal cones ; o, dermal oxea ; p, 

 pore. 



Pig. 3. Longitudinal section: r.c., radial chamber; d, chamber dia- 

 phragm ; o, dermal oxea ; c, distal cone. 



Pig. 4. Transverse section : i, inter-canal. 



Pig. 5. Section across tubes and inter-canals: r.c., radial chamber; 

 i, inter-canal. 



Pig. 6. A prosopyle, surrounded by collared cells. 



Pig. 7. Unsegmented ovum. 



Pig. 8. Ovum subdivided: ex., collared cells; ex., endothelial cells. 



Pig. 9. Three segmented ova in a common capsule (the ovum on the 

 right was damaged, and I have not shown it in section) : ex., 

 collared cells ; ex., endothelial cells. 



Pig. 10. Longitudinal oxea of dermal surface. 



Pig. 11. Oxea of cones. 



Pig. 12. Oxea of peristome. 



Pig. 13. Sagittal 3-radiates of chamber-layer. 



Fig. 14. Irregular 3-radiates of chamber-layer. 



Pig. 15. 4-radiates from gastral cortex. 



Pig. 16. Two collared cells, with flagellum retracted, and an amoeboid 

 cell. 



