PTEROBRANCHIA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 563 



ments, four individuals of C. hodgsoni, of both sexes and in varying degrees of con- 

 traction, measured from ]'568 to 1'856 mm. Four individuals of C. inaequatus, 

 similarlv measured, fell within the limits 1760 to 2240 mm. The longest of these 

 zooids in particular was obviously well extended. It may accordingly be concluded 

 that while, on the whole, the zooids of the material collected by the Swedish Expedition 

 are rather larger than those obtained by the Discovery, there is no essential difference 

 in size between the zooids of the two forms under consideration. 



Similar results were obtained by a study of the length and thickness of the noto- 

 chord, the size of which Andersson claims to be of some taxonomic value (07, p. 60). 

 The measurements taken from sections of C. insequatus are on the whole greater than 

 those of C. hodgsoni, but the two series of measurements overlap. 



The buds of C. insequatus were examined to see if there is any appreciable difference 

 between them and those of C. hodgsoni (Ridewood, 07^, p. 225), particularly in respect 

 of the mode of development of the arms. In size and general proportions, and in the 

 mode of development of the arms, the two sets of preparations are in very close 

 agreement. 



We are accordingly of opinion that C. insequatus should be regarded as a synonym 

 of C. hodgsoni. 



REFERENCES. 



(07) Andersson, K. A., "Die Pterobranchier der Schwedischen Siidpolarexpedition, 1901-1903," Wiss. 



Ergehn. Schwedischen Siidpolar-Expedition, Bd. v., 1907, pp. 1-122, eight plates. 

 (12) Gravibr, Ch., " Sur une espece nouvelle de Cephalodisciis {C. Anderssoni, nov. sp.) provenant de la 



seconde Expedition antarctique frangaise," Bull. Mus. Hist. nat. Paris, 1912, No. 3, pp. 1-5, 



two text-figures. 

 (87) Harmer, S. F., Appendix to Report on Cephalodiscus, " Challenger" Rejwrts : Zool., vol. xx. pt. Ixii., 



1887, pp. 39-47, four text-figures. 



(97) "On tlie Notochord of Cephalodiscus," Zool. Anzeiger, xx., 1897, pp. 342-346. 



(05) "The Pterobrarichia of the Siboga Expedition, with an Account of other Species," Resultats des 



Explorations entreprises aux Indes Neerlandaises Orientales en 1899-1900 a bord d.u " Siboga," 

 livr. xxii., Monogr. xxvi. bis, Leiden, July 1905, pp. 132, fourteen plates and two text-figures. 



(05) Lankester, E. R., "On a New Species of Cephalodiscus (G. nigrescens) from the Antarctic Ocean," P^-oc 

 Roy. Soc. London, 1905, vol. Ixxvi. B, pp. 400-402, one plate. 



(87) M'Intosh, W. C, "Report on Cephalodiscus dodecalophus," "Challenger" Reports: Zool., vol. xx. 

 pt. Ixii., 1887, with Appendix by S. F. Harmer, pp. 48, seven plates and six text-figures. 



(971) Masteeman, a. T., "On the Diplochorda: II. The Structure of Cephalodiscus," Quart. Journ. Micr. 

 Set., N.S., xl. pt. ii., 1897, pp. 340-366, four plates. 



(972) "On the 'Notochord' of Cephalodiscus," Zool. Aiizeiger, xx., 1897, pp. 443-450, five text- 

 figures. 



(98) "On the further Anatomy and the Budding Processes of Cephalodiscus dodecalophus," Trans. 



Roy. Soc. Edin., xxxix. pt. iii., Dec. 1898, pp. 507-527, five plates. 



(99) "On the 'Notochord' of Cephalodiscus," Zool. Anzeiger, xxii., 1899, pp. 359-363. 



(03) " On the Diplochorda : IV. On the Central Complex of Cephalodiscus dodecalophus," Quart. 



Journ. Micr. Sci., N.S., xlvi., 1903, pp. 715-727, two plates. 

 TKANS. ROY. SOC. EDIN., VOL. XLIX. PART III. (NO. 7). 74 



