68 DISCOVERY REPORTS 



Other characters might help to distinguish the two species, but the accounts of P. detorta by Sluiter 

 (1904) and van Name (19 18) differ with regard to these characters. Thus the very wide and strong 

 sphincters on the oral and atrial openings of P. kottae are characteristic. According to van Name (19 1 8) 

 the corresponding muscles of P. detorta are slender, but Sluiter (1904) describes them as strong, 

 although his figure gives no suggestion of this. 



The orientation of the thorax and the great development of the abdomen in P. detorta and P. kottae 

 are features deserving notice. The structure of P. kottae can be derived from the unspecialized type of 

 Clavelina through a stage like that represented by Podoclavella cylindrica. In this series (Text-fig. 17) 

 two processes have been involved: (1) the formation of a stalk, and (2) unequal growth of the dorsal 

 and ventral sides of the thorax. The former process led finally to the enclosure of the abdomen within 

 a very long narrow stalk with the consequent elongation of the oesophagus and rectum. The latter 

 process has shifted the oral siphon down towards the stalk and at the same time drawn the oesophageal 

 mouth up towards the still terminal atrial siphon. 



Distribution. North Island, New Zealand. 



Genus Clavelina Savigny, 18 16 

 Clavelina claviformis (Herdman) (Text-fig. 18; PI. II, fig. 2) 



Colella claviformis Herdman, 1899, p. 67, pi. Dist. 3, figs. 1-15. 

 Clavelina sigillaria Michaelsen, 1924, p. 269, figs. 1-4. 

 Clavelina claviformis Kott, 1957, p. 88, fig. 22. 



Occurrence. St. 929: North Island, New Zealand, 58-55 m. 



Colony (PL II, fig. 2). Two examples are present in the 'Discovery' collections, from the same 

 station and probably derived from the same group of colonies. One specimen is a single stalked head, 

 and the other consists of a group of about twelve stalked heads attached to a common base. The 

 largest of these has a head 11 cm. long on a stalk of 8 cm., and the smallest is less than half that 

 size. In outline the head is ovate to lanceolate, and is sometimes slightly compressed, but this may be 

 an artifact. The stalk is narrower than the head and is of uniform diameter down to the base. Both the 

 head and the stalk are semi-transparent or pale grey, smooth and without any encrusting matter. The 

 common test is tough and cartilaginous, but the surface has a slimy consistency. The zooids show 

 through the test quite clearly. 



Zoom (Text-fig. 18 A). The thorax is shorter and usually wider than the abdomen, especially when 

 contracted. One typical zooid had a thorax 17 mm. and an abdomen 3-0 mm. long. The two siphons 

 are of almost equal length, and are close together at the anterior end of the thorax. They have circular 

 openings with lobes scarcely marked or entirely wanting. The body wall of the thorax has a series of 

 nine to eleven prominent longitudinal muscles which, passing up from the abdomen, diverge as they 

 approach the anterior part of the thorax, where they generally divide into a few branches. The more 

 ventral muscles of the series diverge towards the ventral margin of the thorax, recalling the course of 

 the muscles in Tylobranchion. 



Branchial sac. From twelve to twenty long slender simple oral tentacles are present in a single 

 circle. The dorsal tubercle is small, with a narrow transverse oval slit. In some zooids the branchial 

 sac has nine rows of stigmata, but more often there are ten to twelve complete rows and two or three 

 short anterior rows, each consisting of a few stigmata in the dorsal part of the branchial sac and none 

 in the ventral part. There are up to forty-five stigmata in the complete rows. The dorsal languets are 

 pointed and moderately long, those at the posterior end being the longest. 



Gut. The long narrow oesophagus passes down to the stomach which lies in the posterior third 



