854 " THETIS " SCIENTIFIC RESULTS. 



exceedingly delicate and hyaline, disc-like in shape, with th& 

 inner edge somewhat strengthened (PI. Ixxxix., fig. 5). Their bases 

 are connected by means of a chitinous ridge with the upper 

 edges of the lateral sarcothecse. The numbers and position of 

 the sarcothecse vary slightly. Thus the superior pair of bithalamic 

 sarcothecse on a hydroclade internode may be replaced by a single 

 median individual — a variation which I have seen present in 

 three out of four hydrothecse on one hydroclade. A similar 

 variation occurs in the sarcothecse on the proximal internode of 

 the secondary hydroclades, and explains the divergence which 

 Billard points to, between his own observation of two opposite 

 sarcothecae, and that of Bale, who mentions only one. 



Dimensions. — 



Hydrotheca, length 0-26-0-28 mm. 



,, diameter at mouth 0"23-0'25 ,, 



Internode of primary hydroclades, length*'^ 0'52-0"66 ,, 



,, of primary hydroclades, diameter 0"25-0-31 ,, 



,, of secondary hydroclades, length ...... 0'46-0'49 ,, 



,, of secondary hydroclades, diameter ... 0'12-0"14 ,, 



Remarks. — In spite of differences between this specimen and 

 the descriptions by Billard and Bale, identity with Plumularia 

 sulcata has been confirmed, on further examination of Lamarck's 

 type, kindly undertaken by the former at my request. This 

 examination. Dr. Billard informs me, reveals, as described above, 

 the hitherto unrecorded presence of a hydrotheca on the oblique 

 internode at the base of each pinna, and of a double series of 

 sarcothecse on the fascicle tubes, both of which characters had 

 been obscured by the delapidation of the original specimen. 



Locality. — Station 48, o£f Wollongong, seven to eight miles 

 from shore ; depth, 55 to 56 fathoms ; bottom, sand and mud tO' 

 rock; 18th March, 1898; a single fine colony. 



Distribution. — Mers australes (Lamarck) ; Broughton Islands, 

 25 fathoms (Bale). 



DIPLOCHEILUS MIRABILIS, Allman. 



Diplocheilus mirabilis, Allmaa, Rep. "Challenger" Exped., vii,,. 

 Hydroida, Part i., 1888, p. 49, pi. viii., figs. 4-7. U.^ 

 Stechow, Abh. K. Bayer. Akad. Wissensch., 1 Suppl. Bd.,, 

 1909, p. 89. 



4:6 Owing to the impossibility of defining internodes in the primary 

 hydroclades, this measurement is made from any point of a hydrotheca to- 

 the corresponding point of the next hydrotheca. 



