A COLLECTION OF HYDROIDS. 297 



Length, measured parallel to abcauline surface, is about 

 0"420 mm., and greatest breadtli 0"230 mm. 



Hydranth. — It has the typical structure. Tentacles, 

 about 24. Nematocysts are small and narrow ; they tend to 

 be especially abundant at the tips of the tentacles. Length 

 5"l/i, and breadth l*l/i. 



GrONOSOME. — Gouangia ovate, but smaller and less elongated 

 than in S. polyzonias. The whole surface is generally 

 ridged transversely by 7-8 rugas. In the female (text-fig. 5, D) 

 the opercular surface is wide and nearly flat, and there are 

 no obvious teeth ; in the male the neck is very narrow, and 

 the teeth, of which there are three, are well developed. 



Length of male gonangium about l"25mm., breadtli 0'75mm. ; 

 length of female 1"35 mm., breadth 0"69 mm. ; thickness of 

 perisarc 16/^*. 



(13) Sertularella tumid a sj^ n. 



A species of hydroid, very closely allied to Sertularella 

 gayi {Lamoi(roux) , Avas dredged from a depth of 40 fathoms 

 about sixteen miles north-east of Bird Island, near Algoa 

 Bay. In addition to these specimens there was picked up on 

 the shore near Park Eynie, Natal, a loose stem of a hydroid 

 which is regarded as the same as that from Bird Island, 

 although there is a slight difference in the curvature of the 

 free adcauline surface of the hydrotheca (text-fig. 6,^ and C). 

 The specimen from Park Eynie, which had doubtless been 

 thrown up on shore from some depth, was richly sup])lied 

 with gonangia, while there were none on the specimen from 

 Bird Island. 



The description given by C. C. Xutting^ for S. gayi will 

 apply with slight modification. 



Teophosome . — Hydrorhiza unknown. 



Hydrocaulus. — Colony straggling in habit, and attaining 

 a height of about 4 inches. Stem fascicled (/.*•.), being made 



' Nutting, C. C, ' American Hydroids, Part II. '• The Sertulavidte," 

 1904, p. 78. 



