CATALOGUE OF TUNICATA. 87 



cells, nor vessels are visible. Many small, round test cells are present in 

 the matrix. The outer layer is, as usual, firmer than the rest. 



Ascidiozooids about 3 mm. long, set at right angles to the surface. 

 Thorax 1 mm. long, abdomen nearly twice as long, post-abdomen very 

 short (fig. 12). 



Mantle very thick, opaque, contracted. Most of the muscle bundles 

 on the thorax are longitudinal, only a few feebler ones run transversely. 

 The branchial aperture is distinctly 6-lobed ; the atrial aperture has no 

 perceptible languet. 



Branchial sac rather opaque in its contracted state. Stigmata about 

 as wide as the inter-stigmatic vessels ; they get much smaller towards 

 the ventral edge of the sac (fig. 13). Muscle fibres run along the trans- 

 verse vessels. 



Tentacles, 20 ; 5 larger, with 3 smaller ones alternating with each 

 larger (fig. 14). 



Alimentary canal with a narrow ossophagus leading to an oval, thick- 

 walled, but smooth stomach. The intestine is narrow where it leaves 

 the stomach, but soon widens. It is narrower again at the posterior 

 end, where it turns anteriorly ; and then widens to become the rectum, 

 which passes along the ventral edge of the stomach, and then crosses the 

 oesophagus to end on the dorsal edge of the thorax (fig. 12). 



The gonads lie in the very short post-abdomen, and have both ova and 

 spermatic vesicles. There are large tailed larvae in the peribranchial 

 cavity. 



Locality. Port Jackson ; one colony and a fragment. 



Psammaplidium incrustans, Herdman,* PI. Pel. VI., figs. 1 6. 



Colony thin and encrusting, with a few irregular lobes arising from its 

 surface (fig. 1). No Ascidiozooids on the lower attached surface, which 

 is covered with fragments of foreign bodies. Upper surface sandy, while 

 a middle layer of test between is free from sand, and of a blue grey 

 colour (fig. 4). Surface of colony rough with sand ; colour, sandy grey. 

 Length about 8 cm., breadth about 3'5 cm., thickness about - 5 cm. 



Test with much imbedded sand on the upper and lower surfaces. 

 Numerous small test cells are present, but no pigment cells, bladder 

 cells, nor vessels. 



Ascidiozooids about 3 mm. long, placed at right angles to the surface. 

 Abdomen rather longer than thorax, and post-abdomen much shorter 

 (fig. 5), in some cases practically absent. 



* "Revision," 1891, p. (520. 



