DE. W. A. HEEDMAN ON BEITISH TUNICATA. 289 



vertical extent greatest, with large conical papillae at the corners 

 and no intermediate ones. Stigmata oblong with rounded ends, 

 usually two in a mesh. 



Dorsal lamina ribbed transversely ; margin irregularly pectinated. 



Tentacles numerous, placed close together, about 20 large and 

 the same number of rather small intermediate ones. 



Olfactory tubercle irregularly U-shaped ; opening anterior, wide. 



Viscera rather small, seen distinctly through mantle on left side. 

 Stomach large, yellow. Intestine narrow, black. 



Locality. Lamlash Bay, 10 fathoms, Sept. 1879. 



P.S. — In connection with the irregular branchial sac oiAscidia 

 scabra (see PL XVII. fig. 3) mentioned on page 281, I have un- 

 fortunately omitted to refer to Lacaze-Duthiers' interesting 

 description of three varieties in the branchial sac of Ctenicella 

 Lanceplaini (Arch. Zool. exper. vol. vi. p. 619, 1877). But I 

 hope to return to this subject in a future communication. 



EXPLANATION OF THE PLATES. 

 Plate XIV. 



Fig. 1. Ascidia lata, n. sp. Seen from the right aide, natural size. 



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



3. The same. Olfactory tubercle, magnified. 



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



5. The same. Part of branchial sac, from the inside, magnified. 



6. The same. Olfactory tubercle, magnified. 



Plate XV. 



Fig. 1. Ascidia virginea, O. F. Miiller. Part of branchial sac, seen from 

 inside, magnified. 



2. The same. Part of branchial sac, seen from outside, magnified. 



3. Ascidia truncata, n. sp. Seen from right side, natural size. 



4. The same. Part of branchial sac, seen from inside, magnified. 



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



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



Plate XVI. 



Fig. 1. Ascidia aspersa, 0. F. Miiller. Part of branchial sac, seen from 

 inside, magnified. 



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



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



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

 LIJSN. JOUEN. — ZOOLOGY, VOL. XV. 22 



