6 THE AUSTRALIAN MUSEUM 



Stereoclavella,* Herdman, 1890. 



Colony with the stolons united in a basal thickening or mass of test. 

 Body not pedunculated, apart from the long abdomen, which is distinct 

 from the thorax. Branchial and atrial apertures circular, not lobed. 



Test on the body thin, thicker and cartilaginous posteriorly, where it 

 forms the stolonial basal mass. 



Mantle thin. 



Branchial sac with no internal longitudinal bars. Transverse vessels 

 all equally wide. 



Visceral viass forming a distinct abdomen as large as the thorax. 



There are four known species in the genus, S. (Clavelina) oblonga, 

 Herdm., from the Atlantic, and Si (Clavelina) enormis, Herdm., from 

 the South Atlantic, both obtained during the " Challenger" Expedition, 

 in addition to the two described below. Garstang's Pycnoclavella 

 aitiiluceus, from Plymouth, must be a closely related form. 



Stereoclavella australis, Herdman (1891), PI. Clav. I., figs. 1 11. 



External appearance,. The colony tassel-shaped, consisting of a 

 large number of Ascidiozooids united together in clumps on the summit 

 of a solid stalk-like mass of test. Free ends of the Ascidiozooids 

 cylindrical, truncated anteriorly, where both apertures are placed not far 

 apart. Colony about 9 cm. in length, and 5 to 6 cm. in breadth at the 

 broadest part, and 3 cm. in thickness at the same place. The average 

 thickness of the basal solid test is 2 cm., and its length about 5 cm. 

 Surface smooth, colour grey. 



Test thin over the thoracic, free, part of the Ascidiozooid, thicker over 

 the abdomen, gradually passing into the very thick solid basal mass. 

 Abundance of small test cells in all parts. Over the abdominal part of 

 the body small and very slender unbranched spines project from the 

 surface of the test : each has a test cell at its base. Solid basal part of 

 test with numerous stolonial blood vessels running in all directions and 

 giving rise to many buds. 



Mantle with about 6 very distinct longitudinally running muscle 

 bands on each side of body, on the thorax. These spread out and 

 become more numerous on abdomen. Body of Ascidiozooid nearly 2 

 cm. long and about 5 mm. wide in the thoracic part Thorax globular, 



* Briefly defined for the reception of the two " Challenger" species Clavelina oblonya 

 and C nun-mis, along with the present species, in Trans. Biol. Soc., L'pool, vol. V., pp. 

 160161 ; and also in "Revision," Jour. Linn. Soc., Zool., vol. XXIII., p. 603. 



