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THE VOYAGE OF H.M.S. CHALLENGER. 
secoud Ascidiozooid represented in the figure shows an ovate stomach with the long 
axis antero-posterior, and the posterior end narrow. In transverse sections the lumen 
of the stomach is seen to be cruciform (PI. XLI. fig. 2, st.). This is produced by 
the presence of four longitudinal pads of thickened epithelium. The intestine is 
long. It runs posteriorly from the stomach and then turns ventrally in rather a 
wide curve, and before turning anteriorly it becomes more or less distinctly thickened 
for a short distance (PI. XLI. fig. 2, where the Ascidiozooid at the left side of the figure 
shows the thickening more than usually distinct, and forming a considerable enlargement 
on the intestine). From this point the rectum runs anteriorly and dorsally so as to 
reach the oesophagus which it crosses. The intestinal loop is wide. 
The testis, in the form of a single large ovate mass (PI. XLI. fig. 2, t.v.), was 
present in some of the Ascidiozooids examined, but no ova and no embryos were dis- 
covered in any part of the colony. 
Leptoclinum thomsoni, n. sp. (PI. XLI. figs. 1, 5-7). 
The Colony is an irregular mass, incrusting and rather flat. The surface is moderately 
even and smooth. The colour is opaque white. 
The length is about 2 cm., the breadth about 0'7 cm., and the thickness 2‘5 mm. 
The Ascidiozooids are numerous but small. They are distributed evenly over the 
surface of the colony, and are not arranged in regular systems. No common cloacal 
apertures are visible. The body of the Ascidiozooid is divided into two distinct regions, 
thorax and abdomen. 
The Test is hard and firm. It is of a creamy white colour, and is quite opaque. In 
sections the clear structureless matrix is seen to contain a few delicate test cells and a 
large number of calcareous spicules. The spicules are fairly large, and are of very regular 
stellate form. In some places they are densely crowded. 
Tlte Mantle is rather muscular. It has both longitudinal and transverse bands. 
The Branchial Sac is moderately large. It has three or four rows of large stigmata 
which are arranged with regularity. The transverse vessels are provided with muscle 
fibres. 
The Endostyle is large and conspicuous. Its course is greatly convoluted. 
The Dorsal Lamina is represented by a series of languets. 
The Alimentary Canal is large. The stomach is fusiform and smooth- walled. 
Locality. — Unknown. 
Some colonies of this species were found attached to Algae, along with specimens of 
Leptoclinum campenteri, during one of the cruises of the “ Porcupine.” The exact 
locality is unknown. 
