626 PEor. w. A. heedmak's eetised 



Test gelatinous, not sandy. 



Branchial sac large and well developed. 



Alimentary canal large. Wall of stomach areolated or irre- 

 gularly thickened. 



Postahdomen large, but not distinctly separated from the 

 abdomen by any constriction. 



MorcTiellioides contains two species, which may be distinguished 

 as follows : — 



(With muscle-fibres in the transverse vessels ; branchial lobes rounded. 

 M. affinis, Herdm. (A. Arct.) 

 No muscle-fibres in vessels ; branchial lobes pointed. 

 M. Alderi, Herdm. (N.W. Eur.) 



Paeascidia *, Milne-JEdwards, 1842. 



Colony massive, attached. 

 Test gelatinous. 



Ascidiozooids having thorax, abdomen, and postabdomeri. 

 Branchial aperture 8-lobed. 



Branchial sac with no internal longitudinal bars and no papillae. 

 Alimentary canal with stomach areolated or pseudo-areolated f. 

 Bostahdomen separated from abdomen by a constriction. 

 This group has had the following 4 species referred to it : — ■ 



f Colony fan-shaped, pedunculated, lobed, orange. 

 P. flahellata, Aid. (N.W. Eur.) 

 Colony globular or foi'ming a flattish expansion 1 



I /Colony small, globular, pale yellow... P. ^rtw^WjM.-Edw. (N.W.Eur.) 



\ Colony large, flat-topped or lobulated 2 



f, f Amber-coloured P. Forhesi, A\d..\ (N.W.Eur.) 



^[Palered P. i^ifm^^i, Ald.|(N.W.Eur.) 



Ekagaeium, Giard, 1872. 



Colony massive, attached. 



Systems compound ; large common cloacal aperture with 

 denticulated margin. 



Ascidiozooids having thorax, abdomen, and' postabdomen. 

 Branchial aperture 8- (may be 6-12-) lobed ; atrial anterior. 



* Lahille states that this genus vpas intended by Milne-Edwards to include 

 forms with the stomach-wall longitudinally iolded, and that therefore it is 

 synonymous with the genus i^ra^'anwm of Giard. I believe it will causeless 

 confusion to leave the definitions of these groups as they now are. 



t The thickenings being in the form of longitudinal iblds broken up into 

 little knob-like or ellipsoidal projections. 



X These may possibly be one species. 



