HYDJx'OIDS EASTERX CAXADA 337 



SESSIONAL PAPER No. 38a 



tiou of the hydroids in use, we have, to use Levinsen's words, '' incommensurables 

 defined by different laws, so that we must have the logical sequence, that one of them 

 cannot be substituted for the other." 



While, therefore, the care with which Levinsen did this work on the opercular appa- 

 ratus is fully recognized and while the value to systematists of this exhaustive examina- 

 tion is in no way under-estimated, it is impossible to do otherwise than conclude as many 

 others have done, that although the nature of the opercular apparatus is a good char- 

 acter and is of much value in classification, it cannot be used satisfactorily as the 

 sole basis on which to divide the Sertularidae into genera. The time may come when 

 there will be more general agreement on the method of classifying this family but it 

 will be at a time when all the main variable features of each species will be taken into 

 consideration. 



As this paper is on distribution rather than on taxonomy, it is not desirable to 

 discuss in detail this or any other system of classification. By adhering to the nomen- 

 clature used throughout in previous papers for the Sertularidse as for the other fami- 

 lies, there will at least be no difficulty in following the references to the various species 

 considered. 



Sub-order GYMNOBLASTEA. 



Family CLAVIDJE. 



Genus COEDYLOPHORA. 



CoRDYLopHORA LAcusTRis Allman. 



Cordylophora lacusiris Allmax, Ann. and Mag. ISTat. Hist., 1st ser. viii., 1844, 



p. 330. 

 HiNCKS, Br. Hydroid Zoophytes, 1868, p. 16. 

 Stafford. Fauna Atlantic Coast, 1912, p. 72. 

 Distribution. — St. Andrews, Gaspe, Se%'en islands (Stafford). 

 Although this is a fresh- or brackish-water form, since it has been reported it is 

 well to include it in the list. 



Genus CLAVA. 

 Olava leptostyla Agassiz. 

 Clava multicornis Stimpson, Marine Invert. Grand Manan, 1853, p. 16. 

 Clava leptostyla Agassiz, Cont. Nat. Hist. U.S.. vol. iv, 1862, p. 218. 

 HiNCKS, British Hydroid Zoophytes, 1868, p. 6. 

 Nutting, Hyd. Woods Hole. 1901. p. 321. 

 Hargitt, Am. Xat. 1901, p. 305. 

 Whiteaves, Mar. Invert. East. Can., 1901, p. 18. 

 Stafford, Fauna Atlantic Coast, 1912, p. 72. 

 Fraser, Hyd. Nova Scotia, 1913, p. 159. 

 Distribution. — Salmon Bay (Packard) ; Long island point to Labrador ( Verrill) ; 

 St. Andrews, Canso, Seven islands (Stafford) ; Canso (Fraser) ; St. Andrews. 



Family LABID.E. 

 Genus MONOBRACHIUM. 

 MoNOBRACHiuM pARAsiTUM Meveschlcowshy. 

 Monobrachium parasitum Mereschowsky, Hyd. from White Sea, 1877. p. 226. 



Levinsen, Medusae, Ctenophorer, etc., 1893, p. 151. 

 parasiticum Bonnevie. Norske Nordhavs-Ex.. 1899, p. 151. 

 parasitum Stafford, Fauna Atlantic Coast, 1912, p. 73. 

 Distribution. — Gaspe ( Stafford) . 



