HYDROZOA — RITCHIE. 839 



tion of the coenosarc permitted discrimination to be made, the 

 gouangia were found to contain large ova, about five in number. 



Dimensions. — 



Stem internode, greatest length 1 22-1 -36 mm. 



Pinna, diameter 0"42 mm. 



Hydrotheca, length 39 mm. 



HydrothecH, diameter 0-16-018 mm. 



Gonangiura, length 2 mm. 



Gonangium, greatest breadth (frontal aspect) ... 0'G4-0 73 mm. 



Gonangium, greatest breadth (lateral aspect) ... 0"52-063 mm. 



Affinities. — This species, which belongs to the Johnstoni-group 

 of Hartlaub, seems to be most closely allied to Seriularella 

 pluma, Hartlaub, but fiom that it may be distinguished by the 

 greater length of its pinnae (at least twice as long) ; by the 

 presence of a pinna on each internode, by the wider angle at 

 which the pinnae are set, and especially by the shape and habit 

 of the gonangium. 



There is much superficial resemblance also to SertulareUa 

 suharticidata (Cough trey), an undoubted Sertidarella, hitherto 

 referred to TJmiaria by authorf. In this case, however, Cough- 

 trey, Allman (who described the species under the name Thuiuria 

 bidens), and Bale, each describe the hydiothecse as having two 

 adcauline teeth, although the last adds that " it is often difficult^ 

 to distinguish more than one tooth on the inner side."^^ 



In Sertularella adpressa, the single adcauline tooth is unmis- 

 takable and invariable. There are great difierences between 

 these species, also, in the structure and habit of the gonangium. 



Localities. — Station 36, off Botany Bay, one mile from shore; 

 depth, 23 to 20 fathoms; bottom, sand to rock; 11th March, 

 1898; young colony without gonangia. Station 54, within 

 Jervis Bay; depth, 10 to 11 fathoms; bottom, seaweed and 

 sand ; 20th March, 1898; large colony with gonangia. 



Type Specimens. — In the Australian Museum, Sydney. 

 SERTULARELLA DIVARICATA (Busk), 



var. SUBDICHOTOMA, Bale. 



Sertularella suhdichotoma, Kirchenpauer {in parte), Abh. Nat. 

 Ver. Hamburg, viii., p. 46 {fide Hartlaub, 1900, p. 33). 



3» Bale— Proc. Linn, Soc. N.S. Wales, (2), iii., 18S8, p. 746. 



