DR. W. A. HEEDMA2T OF BEITISH TTTNICATA. 281 



area at the left side of the posterior end. Apertures both on 

 right side ; branchial terminal, placed at the dorsal extremity of 

 the anterior end, and turned dorsally ; atrial close to the bran- 

 chial, and directly posterior to it, being on the right side, close to 

 the dorsal edge, and about one fifth of the way down. Both 

 apertures slightly projecting, tubular, rather wide ; atrial more 

 distinctly and regularly lobed than branchial. Surface rough 

 and irregular, especially on the posterior half of the right side. 

 Several foreign bodies adhering at the base, and some specimens 

 of Modiolaria marmorata imbedded in the anterior half of the 

 right side. Lobes of apertures finely echinated. Colour yellowish 

 grey to dark brown. Length 6*8 centims., breadth 4 centims. 



Test moderately thick, tough ; inner surface smooth, with a 

 bluish tinge ; no vessels visible. 



Mantle well developed ; muscle-bands strong, but rather distant 

 on the right side and round the edges of the left ; entirely wanting 

 over the visceral mass, where the mantle is membranous. 



Branchial sac longitudinally plicated ; every third or fourth 

 transverse vessel larger and more muscular than the intermediate 

 ones. Internal longitudinal bars well marked, borne on long 

 curved ducts, and bearing very small papillae, which merely form 

 slight thickenings at the angles of the meshes. Meshes rather 

 elongated transversely ; stigmata short, elongate-elliptical, six to 

 eight in a mesh. 



Dorsal lamina broad, ribbed transversely, and slightly pecti- 

 nated at the margin. 



Tentacles rather large and strong, 32 in number, longer and 

 shorter alternating. 



Olfactory tubercle regular, broadly heart-shaped ; both horns 

 coiled inwards. 



Viscera reaching as far posteriorly as the base of the branchial 

 sac. 



Locality. Upper end of Loch Long, 5 to 10 fathoms. 



This species is probably allied to A. virginea. 



Ascidia aspeesa, O. F. Muller. (Plate XVI. figs 1-3.) 

 Ascidia aspersa, O. F. Muller, Prodromus, p. 225. no. 2728 (1776); 



Zool Dan. ii. p. 33, tab. 65. fig. 2 (1780). 

 Ascidia mamillaris, Belle Chiaje, Mem. degli anim. di Napoli, vol. ii. 



p. 197, tab. xlv. fig. 14 (1823). 

 Phallusia cristata, Risso, Hist, not, d. prod, de VEur, merid. t. iv. p. 276 



(1826). 



