[s2 THE VOYAGE OF H.M.S. CHALLENGER. 



The Dorsal Tubercle is circular or slightly elongated transversely, one end is turned 

 out and one turned in. 



This is a curiously shaped little species, and like Polycarpa pedata has the posterior 

 end of the body prolonged to form a peduncle (PI. XXIV. figs. 3 and 4). The lower end 

 of the peduncle gives off a number of fine prolongations or rootlets, by means of which 

 the animal is attached. 



The test is rather thick and strong, is not irregular on the surface, but has sand grains 

 attached here and there. The folds in the branchial sac are well marked, and have the 

 internal longitudinal bars closely placed, while in the interspaces they are few and distant 

 (PL XXIV. fig. 5); consequently the meshes are wide, and contain mostly ten or twelve 

 stigmata. The transverse vessels are of two sizes, arranged so that three smaller and one 

 larger alternate. The tentacles are numerous and closely crowded. There are numerous 

 yellow polycarps present. 



In external appearance this species is not unlike Polycarpa pedunculata, Heller, 1 but 

 is much smaller, and differs in several details of internal structure, such as the number of 

 tentacles. 



Two specimens of this species were collected, both in Australia. One is from Port 

 Jackson, depth, 6 fathoms ; the other was trawled off Twofold Bay, south-east coast of 

 Australia, at Station 163; April 4, 1874; depth, 120 fathoms. 



Farudy Ascidiid.e. 



Body fixed ; usually sessile, rarely stalked. 



Test cartilaginous or gelatinous, rarely chitinous. Branchial aperture usually 



eight-lobed ; atrial aperture usually sixdobed. 

 Branchial Sac not folded ; internal longitudinal bars present, and usually papil- 



lated ; stigmata straight or curved. 

 Tentacles simple, filiform. 

 Intestine either placed at one side of the branchial sac, or extending beyond it 



posteriorly. 

 Genitalia always in close connection with the alimentary canal. 



This is a very compact family, its only close allies being the Clavelinidse, from which 

 it is sharply defined by its want of the property of budding. From the other two fanidies, 

 the Molgulidae and the Cynthiidae, it is distinguished by its branchial sac not being- 

 disposed in folds. The remaining characteristics given above, though none of them alone 

 would sufficiently define the family, are all of importance, and when taken collec- 

 tively separate the Ascidiidae from other Simple Ascidians. 



1 Beitrage zur nahern KennUiiss der Tunicaten, p. 24. 



