5o 



DISCOVERY REPORTS 



pieces is 4-5 cm., of which the head occupies about 1 cm. The average lengths are about i-o cm. for 

 the head and 2-5 cm. for the stalk. The head is conical, ovoid, or inverted conical, and has a greatest 

 diameter about twice that of the stalk. The stalk is of uniform diameter except where it expands on 

 joining the head. Both head and stalk have a coating of sand and broken shell, but the coating is 

 thicker on the stalk. The head is fairly soft and the stalk hard. The zooids are arranged roughly at 

 right angles to the surface of the head of the colony. A longitudinal section of the colony shows that 

 the thorax and abdomen of the zooids form a uniform peripheral layer and that the post-abdomens 

 are contained in the core. Sand is relatively scarce in the peripheral layer and densely packed in the 

 core where it occupies most of the space between the post-abdomens. Sand is also abundant within 

 the stalk. 



Zoom (Text-fig. 8B). The thorax averages 3 mm. and the abdomen 1-5 mm. in length; the post- 

 abdomen varies greatly and often extends for many millimetres down into the stalk. When preserved 

 in alcohol the zooids are brown. 



Thorax. The oral siphon is moderately wide and its rim scarcely lobed. The short atrial siphon is 

 far forward, with a small simple opening, and a strap-like bifid languet («./.). There may be a small 

 tooth on the posterior margin of the atrial opening. Nine or ten thin longitudinal muscles pass down 

 the sides of the thorax and condense into a strong band (mus.) which extends to the end of the post- 

 abdomen. The oral tentacles are slender and few, apparently about eight in number. Fourteen rows 

 of stigmata are usual, each with sixteen to eighteen stigmata. The dorsal languets are short and 

 curved. 



Gut. The oesophagus is narrow and curved so that it enters the antero-dorsal side of the stomach. 

 The walls of the stomach are marked by rather few and not very prominent round areolations. 

 Sometimes these are reduced to little more than superficial marks. The anus, which lies opposite the 

 nth row of stigmata, has two distinct lobes. 



Gonads. In none of the zooids was any trace of gonads found, nor were larvae found. 



Remarks. Brewin (1950) pointed out the resemblance between this species and S. arenaceum 

 (Michaelsen, 1924), but maintained that the zooids differ specifically. Table 13 gives a comparison 

 between Brewin's type material, the ' Discovery ' specimens, and S. arenaceum. 



The similarities between the type specimens and those in the 'Discovery' collection indicate 

 that they are of the same species. It is difficult, with the limited material, to decide whether S. are- 

 naceum is a separate species, especially as the ' Discovery ' specimens are in some respects intermediate 

 between the type specimens of S. kuranui and S. arenaceum, e.g. in the number of rows of stigmata. 



