284 DR. W. A. HERDMAN Off BRITISH TITfflOATA. 



Viscera. — -Stomach distinct, nearly globular; intestine rather 

 long and narrow. 



Locality. Lamlash Bay, 10 to 20 fathoms. 



This species comes near Ascidia aspersa. In some parts of the 

 branchial sac (PL XYI. fig. 6) there is an irregularity and want 

 of continuity in the internal longitudinal bars ; the same condi- 

 tion is seen frequently in Corella parallelogramma. 



Ascidia scarra, O. F. Midler. (Plate XYI. fig. 8; Plate XVII. 

 figs. 1-3.) 



Ascidia scabra, 0. F. Muller, Prodromus, p. 225. no. 2726 (1776), Zool. 

 Dan. ii. p. 33, tab. 65. fig. 3 (1780) ; Forbes Sf Hanley, Brit. Moll. 

 vol. i. p. 33 (1853). 



Phallusia scabra, Grube, Die Insel Lussin fyc. p. 55 (1864). 



Ascidia scabra, Hancock, Anat. and Phys. of Tun., Journ. Linn. Soc. 

 Zool. vol. ix. p. 309 (1868). 



Ascidia scabra, Heller, Untersuchungen u, d. Tun. Adriat. u. Mittelm. 

 1 Abth. p. 17, Taf. vi. fig. 13 (1874). 



As far as I am aware only the external appearance of this 

 species has been described ; the following will complete what is 

 necessary for the proper definition of the species. 



Branchial sac longitudinally plicated ; transverse vessels usually 

 all of the same size, occasionally, however, slighter intermediate 

 ones are present for short distances. Internal longitudinal bars 

 distinct, but having no papilla?. Meshes usually transversely 

 elongated, each containing about twelve stigmata. 



.Dorsal lamina broad, ribbed transversely ; margin finely but 

 irregularly toothed, five to seven teeth between each pair of ribs. 



Tentacles of three lengths, 18 long and rather slender, the 

 same number of shorter intermediate ones, and about 36 very 

 short ones, regularly disposed between the others. 



Olfactory tubercle simply oval in outline, the opening at the 

 anterior end ; horns not coiled. 



Ascidia scabra is allied to both A. aspersa and A. virginea. I 

 have figured (Plate XVII. fig. 3) a small part of the branchial 

 sac of one of my specimens, to show the amount of irregularity 

 which may occur j it is seen from the outer side so as to avoid 

 the additional complication which the presence of the internal 

 longitudinal bars would introduce. 



Ascidia patoni, n. sp. (Plate XVII. figs. 4-7.) 



External appearance. — Shape elongate-elliptical ; anterior end 

 narrow, posterior rounded ; dorsal edge more convex than ven- 



