NO. 5 MIDDLE CAMBRIAN ANNELIDS I27 



191 1 material will be discovered that will give mvich better data for 

 determining its family relations. 



Formation and locality. — Middle Cambrian: (35k) Burgess shale 

 member of the Stephen formation, west slope of ridge between 

 Moimt Field and Wapta Peak, one mile (1.6 km.) northeast of 

 Burgess Pass, above Field on the Canadian Pacific Railway, British 

 Columbia, Canada. 



Class GEPHYREA— Quatrefages 



Class II.— GEPHYREA. 



" The Gephyrea are marine Annulata devoid of any trace of seg- 

 mentation in the adult condition, without parapodia, and either 

 without setae or with only a limited number ; with either an invag- 

 inable anterior body region or introvert, at the extremity of which 

 is the mouth surrounded by tentacles, or with a long, highly re- 

 tractile proboscis representing the pre-oral lobe of the larva, and 

 having the mouth situated at the base. The anus is sometimes 

 terminal and posterior, sometimes anterior and dorsal. There is an 

 extensive coelome filled with a corpusculated fluid, and not divided 

 by septa. The ventral nerve-cord is not made up of a series of 

 ganglia. There is, as a general rule, only a single pair of nephridia. 

 The sexes are separate ; the ovaries and testes simple masses of 

 cells ; the nephridia act as reproductive ducts. The larva is a 

 trochophore." ^ 



The genus Ottoia is tentatively referred to the Gephyrea, since, 

 while it possesses certain characters of the Gephyrea, it has others that 

 do not come clearly within the class. The segmentation of the body 

 serves to withdraw it from Gephyrea, but in so ancient a form this 

 character is to be anticipated. The proboscis is similar in function to 

 that of some of the Gephyrea and Polychseta where the buccal region 

 is " everted " and may be withdrawn into the buccal region." The 

 proboscis and mouth of Ottoia also suggest the sucker-like mouth 

 and proboscis of some of the Hirudinea (leeches). The exterior 

 appearance of the body of Ottoia is also not unlike that of some of 

 the leeches that have a slender body, finely marked segmentation, 

 and a retractile proboscis with the mouth at the end. The absence 

 of parapodia removes Ottoia from the Polychseta, and the presence 

 of segments is not sufficient to place it with the Hirudinea. 



^Parker and Haswell, Text-Book of Zoology, Vol. i, London, 1910, pp. 

 491-492. 

 ^ See Cambridge Natural History, Vol. 2, London, 1896, pp. 249-250. 



