DENDY— CALCAREOUS SPONGES 83 



especially more slender than the subgastral sagittals, with the centripetal ray 

 straight and the outer rays more or less bent and asymmetrical. All rays gradually 

 sharp-pointed. In a typical example the centripetal ray measured 0-36 by 0-025 

 mm., and the outer rays apparently 0-24 by 0-025 and 0-17 by 0-025 mm. 

 respectively. 



6. Large oxea (Figs. 7/, 7/', 7/"). These spicules, though not very numerous, are 

 highly characteristic. Their outer ends usually project more or less at right angles 

 from the surface, and often for a great proportion of the length of the spicule, but 

 except over protected areas of the surface they are almost invariably broken off. 

 The form of these spicules affords by far the most characteristic feature of the 

 species, and after a careful study of isolated specimens I am able to add certain 

 particulars under this heading. The entire spicule is sKghtly curved (Fig. 7/'). The 

 inner end is simply sharp-pointed. The outer end is sharp-pointed and flattened 

 Uke a spear-head, with a sharp knife-edge on either side. On one side (the 

 concave side of the spicule) this knife-edge is simply rounded, on the other it is 

 produced backwards, where it meets the cylindrical shaft of the spicule, into two 

 short, conical teeth. The presence of two teeth can only be clearly seen when the 

 spicule is examined edge on (Figs. 7/, If"), and hence only a single tooth, as seen in 

 side view (Fig. 7/'), has hitherto been described. These spicules measure about 0-83 mm. 

 in total length by 0-035 mm. in diameter in the middle, while the spear-head measures 

 about 0-1 mm. in length. 



7. Trichoxea ; long and very slender, typically arranged more or less at right 

 angles to the dermal surface, but so scarce that they can hardly be regarded as an 

 essential constituent of the spiculation. 



Previously known Distribution. Red Sea (Row) ; Providence I., Indian Ocean 

 (Dendy). 



Register Number and Locality. III. 2. Off Dwarka. 



3. Heteropia glomerosa (Bowerbank).— (Plate I., Figs. 3, 3a, 36 ; Plate II., 

 Figs. %a-^g) 



Leuconia, glomerosa Bowerbank [1873]. 



This well-characterised and very beautiful species was first described by Bower- 

 bank in 1873, from dry material collected at Port EUzabeth, South Africa. The type 

 specimen, which is now in the Natural History Department of the British Museum, 

 is a good deal worn, and possibly beach-rolled, and Bowerbank's figure cannot be taken 

 to represent its natural appearance very accurately. The species has not been recorded 

 since its original publication, but it occurs in considerable quantity in Mr. Hornell's 

 collection. Although the locality is so widely separated from that where it was originally 

 found, there can be no doubt as to the identification, which is based upon a careful 

 re-examination of Bowerbank's material. His description and figures are quite in- 



F 2- 



