182 ARTHUR DENDY. 



Vosmaeropsis (fig. 19). 

 In this genus we find (4) at present only three species — V. 

 macera, V. depressa, and V. Wilsoni, — all ot which are in- 

 teresting with regard to their canal system. The canal system 

 is never truly radial and Sy conoid, but the shape and size of 

 the flagellated chambers, and in V. macera (fig. 19) the 

 arrangement also, clearly indicate a condition intermediate be- 

 tween the typical Syconoid and the typical Leuconoid plan ; in 

 other words, a Sylleibid condition. In V. macera, the anatomy 

 of which is represented in fig. 19, the chambers are thimble- 

 shaped, and mostly widely separated from the central gastral 

 cavity ; they communicate with this by wide exhalant canals, 

 into each of which a number of chambers discharge their con- 

 tents. Each chamber has, as usual, whether it be large or 

 small, a number of small inhalant prosopyles, and a single 

 much larger exhalant aperture, guarded by a well-developed 

 diaphragm (fig. 31). Those chambers which lie next to the 

 dermal surface still exhibit a more or less radial arrangement 

 in relation to the central gastral cavity. 



Vosmaeropsis depressa is, unfortunately, known only 

 from a single specimen, so that it is impossible to tell how far 

 the peculiarities of its canal system are constant. There is 

 no single wide gastral cavity, but several large branching 

 exhalant canals converge to a single small osculum situate 

 near the middle of the upper surface of the cushion- shaped 

 sponge. The inhalant canal system is quite irregular, com- 

 mencing in wide lacunar spaces beneath the thin pore-bearing 

 dermal cortex. The flagellated chambers are irregularly but 

 thickly scattered through the thickness of the sponge, with no 

 trace of radial arrangement around a central gastral cavity. 

 They are, however, more or less sac-shaped or thimble-shaped, 

 measuring about 02 by 0'09 mm. This sponge, from the fact 

 that it possesses but a single osculum, probably corresponds 

 to a single individual, but it is interesting to note how the 

 central gastral cavity has become iudistiuguishably merged 

 into the branching system of wide exhalant canals. 



Vosmaeropsis Wilsoni is a large species found abundantly 



