Plate 41. 



Fig. 1. Petrosia testudinaria, var. fistulophora. Specimen, entire, from sta- 

 tion 5254: from the side. X|. 



2. Petrosia testudinaria, var. fistulophora. Specimen, entire, from sta- 



tion 5249: from the side. X}. 



3. Petrosia lignosa. Side view of the vase-shaped sponge. Xv. 



4. Petrosia lignosa, var. plana. From the side. XJ. 



5. Petrosia lignosa, var. plana. From the side. X^. 



6. Petrosia erustata and Discodermia emarginata Dend'y. The Petrosia 



covers a Gorgon i a -like alcyouarian and everywhere shows the aper- 

 tures of the little depressions which lodge barnacles: The Dis- 

 eodermia is the compact mass at the summit. X£. 



7. Petrosia similis, var. granulosa. Sponge seen from one of the narrower 



sides ; oscula in a row. X h. 



511 



