1916. No. lo. THK LOWER CAMBRIAN HOLMIA FAUNA. 29 



Occurrence: Only one impression of the pygidium of this interes- 

 ting form was found, in the Holmia shales at Tomten. (13. XX\"II. 766I. 



Observations: Unfortunately the descriptions of this small, rare 

 trilobite are not exhaustive, and the illustrations are defective; however 

 everything seems to show that the pygidium from Tomten realiy belongs 

 to this form, or in any case is very closely related to it. The dimensions 

 and most important characters closely agree throughout. The Norwegian 

 pygidium appears to be more abruptly abbreviated posteriorly, but this is 

 evidently due to a displacement in the shales, whereby also the left side 

 lias been somewhat indented as compared with the right. Even more 

 important is the circumstance that the anterior border is more abbreviated 

 than in the American specimens; this however may be explained by a 

 compression in the soft Holmia shales. I therefore consider it unnecessary 

 to lay any particular stress on this difference. 



It appears very unlikely that we have here the remains o\ an Agnostus 

 species, since as is well known the laevigatus groups characterise the upper 

 part of the Middle Cambrian. 



In other respects the demonstration of the existence of this form in 

 Norway is of interest ; we need only consider the following facts. An 

 incomplete specimen was first described by Ford in 1872 from the 

 Lower Cambrian at Troy, New York. This original specimen however, 

 was lost, and it was only recently that another almost complete specimen 

 was found in the corresponding beds in another North American region, 

 viz., at Pearl Street, North Weymouth Mass. and was described by Ray- 

 mond. Now the pygidium of a third specimen has been discovered in 

 Norway. This is surely an interesting instance of our deficient and casual 

 knowledge at the present time of the extent of these ancient creatures. 

 A single fragment, found it may be quite by chance, proves that a form 

 which we believed to have had a very limited habitat in realitv existed 

 throughout an enormous area. 



Fam. Ellipsocephalidae Matthew. 



Representatives of this family have long been recognised as very 

 characteristic forms in the Lower Cambrian of Scandinavia. In the Holmia 

 shales at Tomten, too, Ellipsocephalidae play a prominent part. In addition 

 to the ordinary form, which was long since depicted and described as 

 Ariouelliis primaevus Brogger, but which preferably should be called 

 Stremiella primaeva Brøgger, we find at least two other forms in sufficient 

 abundance for us to be able to define and compare them with other and 



