622 PEOr, W. A. HEEDMAN S HEYISED 



{Colony greyisb; postabdomen short . A. lohatum, Sav. (Med., Red S.) 

 Colony yellowish ; postabdomen very long. 

 A. caliculatum, Sav. (N.W. Eur.) 

 {Both transverse and longitudinal muscle-bands very strong. 

 A. crassum, Herdm. (S. Atl.) 

 Musculature not powerful 8 



Q fStigmata very minute and irregular 9 



I Stigmata normal 10 



q r Colour dark grey A. despectum,'E.evAm. (N. Atl.) 



\ Colour dark smoke-brown A.fuimgatum, Herdm. (A. Arct. 



[& Mai.) 

 ,.-> / With yerj slight grooves on stomach. AJeuco]}h(Eiim,'Kei'dm.. (A.Arct.) 



\ Grooves of stomach-wall well marked 11 



-|^ r Grooves few, 4 to 6 12 



\ Grooves numerous, 10 or more 13 



■jn /Colony sandy A. ffibbulosum*,SaiT. (Med.) 



^^ I Not sandy 14 



1^ /With only 6 rows of stigmata A. griseum, Lah. (Med.) 



\ With about a dozen rows of stigmata. A. effiisum, Sav. (Red S.) 



|o /Colony somewhat sandy on surface... A. incrustans, Herdm. (S. Atl.) 



Colony not sandy 15 



Branchial sac pigmented A, csruletim, Lah. (N.W. Eur.) 



Not pigmented A. zostericola, Giard. (N.W.Eur.) 



Amaeoucium, a. Milne-JEdwards, 1841. 



Colony massive, sometimes lobed or pedunculated. 



Systems usually compound and irregular. 



Aficidiozooids elongated. Branchial aperture 6-lobed ; atrial 

 usually provided witli a long languet, placed close to tlie bran- 

 chial aperture. 



Test cartilaginous or gelatinous. 



Sranchial sac moderately developed. 



Alimentary canal of moderate size. Stomacb-wall folded longi- 

 tudinally. 



Postabdomen usually very long. 



The recognizable species of this large genus may be dis- 

 tinguished thus : 



r Systems simple, regular, and with few ascidiozooids. [Eur.) 



\ A. Nordmanni, M.-Edw. (N.W. 



[ Systems compound, irregular, and with many ascidiozooids ; 1 



-. / Stomach folded longitudinally 2 



[ Stomach simply rayed 3 



o / Colony transparent, colourless. . . .. A. crgstallinum,!). Yalle. (Med.) 



\ Colony opaque, coloured 4 



^/Colour white A. ladetim, v. Dr. (Med.) 



\ Colour orange-red A. conicum, Oliti. (Med.) 



* Possibly this species ought to be referred to Amaroucium. 



