CLASSIFICATION 0¥ TUE TLNICATA. 633 



There are two species known to me : — ■ 



( With a group of spicules on each side of thorax. [(Mecl.) 



i D. 2)sei(dolepfocHniim, v. Dr. 



[ With no such thoracic groups of spicules. B. molle, Herdtn. (Mai.) 



DivijOSOMa*, Macdonald, 1858, 



Colon?/ usually thin and incrusting, rarely thick. 



Systems irregular. Common cloacal apertures rounded. 



Ascidiozooids divided into thorax and abdomen. Branchial 

 aperture usually 6-lobed, atrial a simple aperture. 



Test soft, gelatinous, usually transparent, sometimes pigmented, 

 never with calcareous spicules. Containing muscular processes 

 from the ascidiozooids. 



Branchial sac large, with four rows of stigmata. 



Alimentary canal moderately large. Stomach ellipsoidal and 

 smooth-walled. 



Gonads close to the intestinal loop. Vas deferens straight. 



Gemmation pyloric. Larva gemmiparous. 



The following species (?) can be distinguished in the genus 



Diplosoma : — 



/ Branchial aperture 6-lobed 1 



[ Branchial aperture circular, lobes absent or small 2 



(Test pigmented D. spongiforme, Giard. (N.W. 

 [Eur. & Med.) 

 Test not pigmented B. Macdonaldi, Herdm. (S. Atl.) 



, f Colony thin, incrusting 3 



I Colony thick, fleshy 4 



r Larva forms 2 ascidiozooids D. Bayneri, Macdon. (Austr.) 



3i Larva foi-ms 3 ascidiozooids D. crystailinv,m, Giard. (N.W. 



[ [Eur. & Med.) 



^ r Colour grey or dark green J).chammleon,y.Y)v. (Med.) 



I Colour yellow-brown B. carnosum, v. Dr. (Med.) 



The following names have also been used for forms coming 

 under this genus, but are either synonyms of some of tlie above 

 or are so imperfectly known that they cannot be placed : — 



B. gelatinomm, M.-Edw. (N.W. Eur.) 

 B. Listerianum, Delia Valle. (Med.) 

 B. Koehlerianum, Lahille. (N.W. Eur.) 

 B.jmnctatum, Forb. (N.W. Eur.) 

 B. zosteraritm, Jourdain. (N.W. Eur.) 

 B. gyrosum, Grube. (Med.) 

 B. Listen, Lahille. (N.W. Eur.) 



* Including Astellium, Giai-d ; Brevistelliiim, Jourdain ; Psetulodidemnum, 

 Giard. 



45* 



