46 



BRITISH TUNICATA. 



CHANNEL ISLANDS. Guernsey, adhering to the inside 

 of a dead shell of Patella .vulgata ; dredged (Jeffreys 

 fy Norman}. 



First ret'on.l. -Alder & Hancock, 1863 ; coll. Jeffreys 

 & Norman. 



We have seen only one specimen of this well- 

 characterized species ; it is attached diagonally by the 

 greater portion of the left side, and is so much de- 

 pressed that it is quite discoidal in form, but a little 

 transversely elongated. 



The mantle is delicate and transparent, and is 

 minutely papillose on the outer surface, the papilla 

 being scattered and of a clavate form; it adheres 

 slio-htlv to the test, but can be removed with care. 



tj / ' 



FIG. 37. Part of branchial sac of Molgula complanata. Much enlarged. 



37 



in 



The branchial sac (PI. XXIV, fig. 4, and fig. 

 text) is co-extensive with the body, and is consequently 

 pretty-regularly oval. The orifices of the branchial 

 pouches on the outer surface are small and elliptic, 

 but distinctly defined. The folds, of which there are 

 six on the right side and seven on the left, are regularly 

 and strongly arched, with the concavity towards the 

 ventral margin, the arch increasing in depth as the 

 folds recede from the ventral margin. The secondary 

 vessels form large, distinct, but somewhat irregular 

 spirals, which seem to centre in the folds, there being 

 only one or two to each pouch ; the meshes are wide, 

 comparatively few, short and simple, but sometimes 

 enlarged into irregular spaces. The radiating vessels 



