CLASS II 



GEPHYREA 



141 



Class 2. GEPHYREA. 



Marine Annelida tvitlwut parapodia and typically devoid of any trace of 

 segmentation in the adult condition. 



The Cambrian genera referred to this class by Walcott differ in certain 

 respects from the Recent members, but with our available information the 

 position here assigned them 

 seems most advisable. Two 

 families, (1) Ottoidae, with the 

 genera Ottoia and Banffia, and 

 (2) Pikaidae, including Pikaia 

 (Fig. 217) and Oesia, all from 

 the Middle Cambrian of British 

 Columbia, are recognised. 



A quantity of supposed 

 worm-borings, trails, impres- 

 sions and other obscure remains 

 have been described from the 

 older Paleozoic formations. 

 The burrows have the form 

 of straight or tortuous tunnels, 

 and are sometimes hollow, 

 but more commonly have been 



filled up by solid matrix. Various names have been applied to them, 

 such as ScolifJms, Arenicola, Histioderma, Planolites, Diplocraterion, Spirocolex, 

 Scolecoderma etc., but they are obviously incapable of precise determination. 

 Arthrophycus Hall, originally described as a plant, Daedalus (including Vexillum 



Roualt) and Taonurus Fisher- 



Fio. 224. 



Nereltes ccmbrensis M'Leay. Cambrian ; Llampeter, Wales. 

 Natural size. 





Ooster {Spifophjton Hall), have 



in recent years been interpreted 



as worm burrows. 



Similarly, the serpentine or 



vermiform impressions known as 

 --a Nereites, consisting usually of a 

 ' ' number of windings, and often of 



profuse occurrence in various 

 Paleozoic formations, were until 

 (|uite recently regarded as worm- 

 trails, or markings made by 

 Fucoids. These also have re- 

 ceived numerous appellations, 

 such as Nereites (Fig. 224), Ne- 

 mertites, Myrianites, Nemapodia, 

 Crossopodia (Fig. 225), Phyllodo- 

 Ordovician ; citss, Naites, etc. Nathorst, how- 

 ever, has brought forward ex- 

 perimental evidence to prove that the majority of these markings have been 

 produced by the movements of Crustaceans, Annelids and Gastropods. A like 

 origin may reasonably be ascribed to the extraordinarily abundant and variable 



Fic. 225. 



Crossopodm {Crossochorda) scotica M'Coy. 

 Bagnoles, Norniandy. 



