APPENDIX A. 



DESCRIPTION OF TWO NEW SPECIES OF SIMPLE ASCIDIANS. 



The two specimens described below wei'e sent tii me after tlie pulilication of the 

 second part of this Report. They Ijoth represent new species, and are referal^le, one to the 

 genus Ahyssascidia in the family Ascidiidse, and the other to the genus Styela in the 

 family Cynthiidse. They were found in the Southern Ocean. 



Ahyssascidia vasculosa, n. sp. (PI. XL figs. 1-6.) 



External Appearance. — The l^ody is of an elongated ovate shape, with the anterior 

 end narrower than the posterior. It is somewhat flattened dorso-ventrally, and was 

 probably attached by a small part of the ventral edge. The apertures are placed far 

 apart. The branchial is anterior and terminal. It is wide and is distinctly eight-lobed. 

 The six-lobed atrial is nearly three-fourths of the way back. It is smaller than the 

 branchial, and is placed on a well-marked tubular projection which is directed posteriorly. 

 The surface is perfectly smooth. The colour is a clear transparent grey. 



Length, 3 cm. ; greatest breadth, 1"5 cm. 



The Test is thin and easily torn. It is smooth and glistening, and is perfectly 

 transparent. It is richly provided with vessels which enter near the posterior end of 

 the ventral edge and branch through all parts. 



The Mantle is not strono;. Its musculature is confined to the right side, where it 

 forms a close but irregular network. The muscle bands are very numerous, but are 

 not strong. 



Tlie Branchial Sac is very delicate. The transverse vessels are all of the same size. 

 The internal longitudinal bars are very narrow. They are joined to the transverse 

 vessels by large triangular flap-like connecting ducts. The papillse at the angles of the 

 meshes are large and of irregular shape. The stigmata are large, and the fine longitudinal 

 vessels are relatively very narrow. There are about four stigmata in a mesh. 



TJie Doi-sal Lamina is a narrow membrane with a deeply cut edge. Every fourth 

 projection is larger than the rest, and is continued across the membrane so as to look 

 like a languet joined to its fellows l)y a serrated web. 



The Tentacles are very numerous and extraordinarily long. They arc of two sizes 

 placed alternately. 



