191 6. No. 10. THE LOWER CAMBRIAN HOLMIA FAUNA. 27 



Cephalopoda. 



Fam. Volborthellidae nov. nom. 



Volborthella tenuis Sch.m. 

 (PI. Ill, figs. 9— 93.1 



1888. Volborthella ttnuis Fr. Schmidt. Ueber eine neuentdeckte unterkatnbrische Fauna in 

 Estland (Mém. de I'Acad. Imp. des Sc. de St. Petersborg, Ser. VIF, Tom. XXXVI, 

 No. 2, Page 25, pi. II, figs. 27 — 311. 



1903. A. Karpixsky, Ueber die eocambrische Cepbalopodengattung Volborthella Schmidt. 

 iVerhandl. d. Russ. Kais. Miner. Ges. in St. Petersburg, Bd. XLI, page 31.1 



Minute description and discussion of the systematic position of this interesting 

 form, with many excellent illustrations. 



Description: The best piece is shown in Plate III. fig. 9, double 

 natural size, and in fig. 9a more strongly enlarged, (xy). The shell is 

 3.3 mm. long, about i mm, broad at the broad end, and 0.75 mm. broad 

 at the narrow end. The former appears to be somewhat compressed, and 

 at the narrow end the section appears to be almost round. F^aint traces 

 of septa are seen on the outer surface. 



Occurrence: Only 7 specimens were found in the Holmia shales 

 at Tomten. In addition to the Mikivitzia sandstone in Eastland, from 

 which this form was first described, it has been discovered at Krasnoje 

 Selo in the neighbourhood of Petrograde, at Lugnås in Wästergötland by 

 G. HoLM^ and in the southern part of New Brunswick in North America, 

 by Matthew-, at the last-named place in the upper part of the Basal 

 Series, and in the lower part of the St. John Group. Finally, it has been 

 shown of late, by Johan Brastad^, to be quite common in the Mjesen 

 region, in the zone with Disciuella Holsti and J ^o/doff/ie//a ft'/iitis just below 

 the Holmia zone. 



Observations: On account of the rather scarce material, I have 

 not been able to demonstrate the septa by grinding; the latter can be seen, 

 — although indistincdy — on the outer side of the specimen depicted. 

 However, the agreement both with Schmidt's and Karpinsky's descriptions 

 and illustrations is so great that I have no doubt about the identification. 

 Moreover, I have had for purposes of comparison one or two specimens 

 from Estland, these being kindly lent by the Riksmuseum at Stockholm. 



' Geol. Foren, i Stockholm Förh. Bd. VII, 1895, page 508. 



- On Cambrian Organismes in Acadia (Transactions of the R. Soc. of Canada, Sect. IV, 



1889, page 156, PI. VIII, figs, 5a— di. 

 3 Discinella Holsti {aumLcn ved Bråstadelven nord for Gjøvik 1 Norsk Geol. Tids. Bd. Ill, 

 1915, page 9, pl- Il fig- 1 — 7' 



