OF THE SPONGIAD^E. 265 



FIG. 



213. BlROTULATE, MARGINS OF THE ROTUL^E ENTIRE. 



From Spongilla gregarea, Bowerbank. A side 

 view of an averaged-sized specimen. X 1100 

 linear. Page 137. 



214. A view of the external surface of one of the rotulae of 



the same form of spiculum as that represented by 

 Fig. 213. X 1100 linear. Page 137. 



215. A young imperfectly developed spiculum of the same 



description as represented by Fig. 213. X 1100 

 linear. Page 137. 



216. A spiculum of the same description as represented 



by Fig. 213, developed to a greater extent than 

 usual. X 660 linear. Page 137. 



217. BlROTULATE, ROTUL^E IRREGULARLY AND DEEPLY 



DENTATE. From Spongilla fluviatilis, Johnston. 

 X 660 linear. Page 136. 



218. A view of the external surface of one of the rotulse of 

 the same description of spiculum represented by 

 Fig. 217. X 660 linear. Page 136. 



219. BlROTULATE: ROTUL^ IRREGULARLY AND DEEPLY 

 DENTATE, SHAFT MEDIALLY SPINED. X 660 



linear. This form occurs in the ovaries of Spon- 

 gilla Meyeni, Carter, from the water-tanks of 

 Bombay. It is the largest spiculum of that form 

 that I have yet seen. It differs from the congene- 

 rous form in Spongilla fluviatilis, inasmuch as the 

 spination of the shaft in Sp. Meyeni is the rule, 

 while in Sp. fluviatilis it is a rare exception. Pages 

 59, 137. 



220. MULTIHAMATE BIROTULATE. X 660 linear. This 

 singular form of spiculum is from the outer portion 

 of the ovaries of Spongilla recurvata, Bowerbank, 

 from the river Amazon. 



The external surfaces of the rotulas are smooth, 

 very convex, and in many cases almost hemispherical ; 

 so that the points of the curved spines are in the di- 

 rection of lines parallel to the shaft of the spiculum, 



