636 PROE. w. A. heedman's revised 



Ascidiozooid having the body divided into thorax and abdomen. 

 Branchial and atrial apertures 4-lobed. 



Two species have been briefly described, but I am unable at 

 present to find any character wbicb will separate tbem : — T. 8yl- 

 vani, Cams (JST.W. Eur.) ; T. Normani, Alder (JN'.W. Eur.). 



PoLTSTTELA *, Giard, 1874. 



Colony consisting of a basal part from whicb tbe ascidiozooids 

 project. 



Ascidiozooids not divided into thorax and abdomen (?). 



Only one species is known, Polystyela Lemirri, Giard, from the 

 coast of France. 



Choeizocoemus, Serdman, 1886. 



Colony consisting of a number of distinct masses of small size 

 united by irregular branched stolons. 



Ascidiozooids placed either singly or in small groups in the 

 test. "When more than one are present, they do not project 

 above the general level. The body is not divided into thorax 

 and abdomen. 



Test relatively small in amount, slightly incrusted witb sand. 

 Test-cells few, and bladder-cells absent. Vessels present in the 

 test and stolons. 



Branchial sac well developed. Eudimentary folds present. 

 Internal longitudinal bars strong. 



Dorsal lamina in the form of a plain narrow membrane. 



Tentacles well developed. 



Alimentary canal not prolonged behind the branchial sac. 



Gonads in the form of polycarps. 



Only one species, CJiorizocormus reticulatits, Herdm., has been 

 described, but I have examined three other new species from 

 Australia, so I include them ia the following table : — 



(With rudimentary folds in the branchial sac. 

 C. reticulatus, Herdm. (A. Aret.) 

 With no rudimentary folds 1 



1 f With more than 20 atrial tentacles. C. Sydneyensis, n. sp. (Austr.) 

 [Atrial tentacles not more than 20 2 



(With 7 rows of stigmata, and 16 branchial tentacles. 

 C. leucopkcEus, n. sp. (Austr.) 

 With 10 rows of stigmata, and 10 branchial tentacles. 

 C. subfiiscus, n. sp. (Austr.) 



* Possibly not distinct frona Thylacium. 



