88 THE AUSTRALIAN MUSEUM. 



Mantle very strong and opaque in its contracted state. 



Branchial sac opaque and corrugated ; stigmata difficult to see ; they 

 are small, and of about the same width as the vessels between them. 

 Strong muscle bundles run along the transverse vessels (fig. 2). 



Dorsal lamina represented by languets, which are not numerous, nor 

 large; they are set about their own length apart (fig. 3). 



Tentacles 10 in number, of two sizes. 



The dorsal tubercle has a simple circular opening in this and other 

 species of Psammaplidium. 



The alimentary canal is rather shorter than usual. A wide oesophagus 

 passes into a smooth-walled, ovate stomach, followed by a thin intestine 

 with no differentiation into regions (fig. 5), and containing oval black 

 pellets of faecal matter. The rectum crosses the oesophagus to reach the 

 dorsal edge of the thorax. 



Gonads formed of masses of globular spermatic vesicles, with a long, 

 thick-walled vas deferens running up the dorsal edge of the abdomen (see 

 fig. 5). No ova are visible. Tailed larvae are present in the peri- 

 branchial cavity. They have a single crescentic, pigmented sense organ, 

 and 3 adhering papillae (fig. 6). 



Locality. Port Stephen ; one colony and some fragments. 



Psammaplidium pedunculatum, Herdman,* 

 PI. Pel. VI., figs. 79. 



Colony in the form of small, sandy, club-shaped masses, consisting 

 of a stalk, with a flattened expansion at its free end (fig. 7). These 

 little clubs are often joined in pairs by the bases of their stalks. The 

 flattened fan-like head consists chiefly of test, with imbedded and 

 encrusting sand grains. The Ascidiozooids do not reach to the free end 

 of the colony in the preserved condition, and lie chiefly in the upper 

 part of the stalk. The colour is sandy grey, the upper end being rather 

 lighter than the stalk. Length 13 cm., breadth 4 mm., width of 

 stalk 2 mm. 



Test small in amount, and very much occupied with sand. There 

 are no bladder cells, pigment cells, nor vessels. The fusiform and 

 spherical test cells are rather large. 



Ascidiozooids about 7 mm. long, and placed parallel to the length of 

 the peduncle. Thorax not so long as abdomen, and post-abdomen very 

 long, in some cases as long as thorax and abdomen together (fig. 8). 



* "Revision," 1891, p. 620. 



