1901. Coi<K. — Observations 071 Oldhamia and Histioder 771a. 83 



annelids, and which seem to illustrate, at any rate, the 

 structure of our own Oldha77iia. His Frcena ra77iosa (p. 159) is 

 described as " clustered passages running mostly in one 

 direction, and spreading as if branched, some raised for a 

 distance of 5 to 10 mm. above the level of the layer on which 

 they occur, others mining the layer .... The passages 

 have a dark skin or coating." The genus Frmia is due to 

 Iyinnarsson ; but Matthew's species, despite its large size, 

 reminds one of the more disjointed specimens of Oldhamia 

 radiata, such as that figured by Dr. J. R. Kinahan 1 in 1858. 

 The most striking traces of annelids that are discussed by Mr. 

 Matthew are, however, those placed under Torrell's genus, 

 Monocraterio7i. The tentacles of Mo7iocraterion tentaculatum, 

 from the Cambrian of Lugnas in Sweden, have a maximum 

 length of 34 millimetres ; those of Matthew's M. mag7iificu7n 

 (p. 160), are "from 8 inches to a foot in length" (200 to 300 

 mm.). Matthew's description is significant, as bearing on 

 what has been said with regard to the constancy of the 

 Oldhamian ridges in successive layers. " In the lapse of time 

 the sand accumulated around the funnel in which the animal 

 lived, making the depressed, trumpet-shaped opening, for 

 which old burrows are remarkable. Their disinclination 

 to change their location is also shown by the constancy with 

 which the tracks of the tentacles maintained their course ; 

 for they scarcely deviated from a certain direction through 

 the different layers of half an inch or more in thickness. It 

 would appear that they did not often turn in their burrows." 

 On p. 161, Mr. Matthew says that the tracks are traceable on 

 successive layers for a thickness of an inch or more. Does 

 not this suggest a magnified example of the phenomena 

 observed in Oldha77iia radiata ? The explanation of the 

 persistence of the markings may, at any rate, be the same in 

 both, whether we accept the reading of Mr. Matthew in 1890, 

 or of Prof. Sollas in 1900. Of course, the burrow is a con- 

 spicuous feature in Monocraterion, while, as Sollas shows, it is 

 obscure, to say the least, in Oldhamia ; but the relative 

 dimensions of the various parts may have differed in genera 

 none the less allied. 



1 Trans. Roy. Irish Acad., vol. xxiii., p. 557. 



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