60 FRISTEDT, OM EN FOSSIL SPONGIA. 



Explanation of the plate. 



Plate XII. 



Fig. a. An adult typespicule of the recurvo-ternate. (^^%). 

 •> b. An abnormous spicule of the same kind with only one, 



bifurcated radius. ("^%)- 

 » c. Also a variety of the same form of spicule with two radii 



and the shaft prolonged as to a third, obtuse radius 



» d. A little locklike fasciculus of spicules, attached to a piece 



of clay. Nat. size. 

 « e. Both the terrainations of one of the long fusilbrmi-acerate 



spicules. Nat. size 6 mm. 

 » /. One of the shorter fusiformi-acerate spicules. (®%)- 

 » g. The middle of a fusiformi-acerate spicule, furnished with 



two bulbous inflations near the middle of the shaft. 



M h. An attenuato-acuate spicule. (^%). 



» i — 1. The three forras of spicules to show their reciprocal lar- 



geness. (^Vi). 



