598 lEOF. W. A. HEEDMAN S RETISED 



Test folded at tlie anterior end, so as to form an operculum 

 covering the apertures. The test is hard and cartilaginous. 



Branchial sac with the stigmata large and straight. 



Dorsal lamina represented by a series of languets. 



Alimentary canal on right side of branchial sac. 



Gonads forming a network round tbe median part of the 

 intestine. 



There are two distinct species known : — 



The dorsal tubercle simple, keyhole-shaped. E. calknse, Lae.-Duth. (Med.) 

 The dorsal tubercle horseshoe-shaped R. pyxis, Traust. (W. Ind.) 



Three other (?) species — R. seminudum, Heller (W. Ind.), 

 B. pellucidum, Stimps. (China), and B. papillosum, Stimps. 

 (China) — require re-examination. 



CiONA* {Savigny, 1816), Fleming, 1828. 



Body cylindrical, attached. Apertures anterior, not distant. 



Test gelatinous or membranous. 



Mantle with the musculature well developed on both sides, 

 forming a few well-marked longitudinal bands. 



Branchial sac witb the stigmata straight. 



Dorsal lamina represented by a series of languets. 



Nerve-ganglio7i and neural gland placed close behind the dorsal 

 tubercle. 



Alimentary canal extending behind the branchial sac. 



Gonads placed on the left side in the intestinal loop. 



(Animals attached in groups by interlocking of viHi from posterior end 

 of test C. fascicularis, Hanc. (N. W. Eur.) 

 Animals separate, solitary 1 



C Body fixed by the whole of left side {Pleurociona, Roule). 

 1 \ C. Edwardsi, Roule. (Med.) 

 [ Body fixed by posterior end or a part of left side 2 



(Transverse vessels all the same size, meshes not divided 

 C. Flemingi, Herdm. (N. Atl.) 

 Transverse vessels of two different sizes, meshes divided horizontally... 3 

 r Test rough with sharp-pointed projections. 



3 i C. aspera, Herdm. (Jap.) 



[ Test smooth, no projections on test 4 



r Fixed by posterior end and short processes of test, siphons unequal ... 5 



4 \ Fixed by part of left side, not posterior, siphons equal. 



y C. Savignii, Herdm. (Jap., Med.) 



r Colour brown, mantle Termilion... G.canina, O.Y.M.. (N.W.Eur.) 

 b\ Colour yellow-green or light grey, mantle same. [Austr.) 



I, C. iniesiinalis, L. (N.W. Eur., Med., 



The following insufficiently characterized species probably 



* Including Pkurocmia, Eoule. 



