290 Dfi. W. A. HERDHAN OS BRITISH TTJNICATA. 



Fig. 5. The same. Seen from left side, natural size. 



6. The same. Part of branchial sac, from inside, magnified. 



7. The same. Olfactory tubercle and tentacles, magnified. 



8. Ascidia scabra, O. F. Miiller. Part of branchial sac, from inside, 



magnified. 



Plate XVII. 



Fig. 1. Ascidia scabra, O. F. Miiller. Olfactory tubercle, magnified. 



2. The same. Part of circlet of tentacles, magnified. 



3. The same. A very irregular part of branchial sac, from outside. 



magnified. 



4. Ascidia Pafoni, n. sp. Seen from the right side, natural size. 



5. The same. Seen from ventral edge, natural size. 



6. The same. Part of dorsal lamina, magnified. 



7. The same. Part of branchial sac, from inside, magnified. 



Plate XVIII. 



Fig. 1. Ascidia muricata, Heller. Part of branchial sac, from outside, 

 magnified. 



2. The same. Olfactory tubercle and tentacles, magnified. 



3. Ascidia obliqua, Alder. Part of branchial sac, from inside, mag- 



nified. 



4. Ascidia depressa, Alder. Part of branchial sac, from inside, 



magnified. 



5. The same. Olfactory tubercle and tentacles, magnified. 



6. Ascidia plebeia, Alder. Olfactory tubercle, magnified. 



7. The same. Another variety of olfactory tubercle, magnified. 



8. The same. A third variety of olfactory tubercle, magnified. 



Plate XIX. 



Fig. 1. Ascidia plebeia, Alder. Specimen with test removed, from right 

 side, natural size. 



2. The same. Part of branchial sac, from inside, magnified. 



3. The same. Part of dorsal lamina, magnified. 



4. The same. Part of circlet of tentacles, magnified. 



5. Ascidia exigna, n. sp. Seen from right side, natural size. 



6. The same. A specimen with test removed, from left side, natural 



size. 



7. The same. Part of branchial sac, from inside, magnified. 



8. The same. Olfactory tubercle, magnified. 



