12 THE AUSTBALIAN MUSEUM. 



In A. pyriformis also the dorsal tubercle is remarkable,* but in a 

 different way. If these two forms turn out to be one species, it must 

 have a very wide range of individual variation in its dorsal tubercle. 



Ascidia phallusioides, n. sp., PI. Asc. II. 



External appearance. The body is oblong, rather wider posteriorly 

 and with a rounded anterior end. It is attached by the posterior end 

 and a small part of the left side. The branchial aperture is near the 

 anterior end, but is recurved so as to point nearly backwards it has 

 about 12 lobes ; the atrial aperture is on the right side of the dorsal edge, 

 near the anterior end, and points forwards it has 6 lobes. The surface 

 is smooth, but marked with deep grooves with rounded edges. There 

 may be little rounded knobs scattered over the surface. The colour 

 varies from a warm yellowish grey to a dark smoky brown. The length 

 is 16 cm., the breadth 8 cm., and the thickness 6 cm. 



Test thick and cartilaginous, firm, of the same colour and consistency 

 throughout, and smooth on both surfaces. Large vessels from the body 

 enter the test on the left side in front of the middle, and branch through 

 all parts. 



Mantle thin, but muscular on the right side. The longitudinal 

 muscle bands are mainly external, and the circular or transverse internal. 

 The anterior part of the left side of the mantle is thinner and less 

 muscular, while the posterior part over the viscera is very thin, and has 

 no muscle bands. 



Branchial sac large and strong, minutely plicated. The transverse 

 vessels differ in size, and there are usually 3 smaller between each pair 

 of larger. The internal longitudinal bars bear very large papillae at the 

 angles of the meshes, and are connected with the transverse vessels by 

 wide membranes. The meshes are elongated transversely, and contain 

 each 6 to 8 stigmata. 



Endostyle large, reaching to posterior end of branchial sac. 



The dorsal lamina is a narrow but strongly ribbed and toothed 

 membrane. The large oesophageal aperture is placed about two-thirds 

 of the way down it. 



The tentacles are not large. They are 36 to 40 in number, and are of 

 two sizes placed alternately. 



The dorsal tubercle, is small and simple. It is placed in a large 

 triangular peritubercular area, continuous with the rather narrow pre- 

 branchial zone. 



* See "Challenger" Report, Part L, p. 220. 



