gS OLAF HOLTEDAHL. M.-N. Kl. 



obtaining with growth». What is impHed here, if not said directly, viz. 

 that the Strophonellas are not to be regarded as a further development of 

 the Strophomenas, is expressed by Schuchert in the classifications of 

 the Brachiopoda, given on various occasions, ^ the genus Strophonella 

 being here placed under the subfamily Rafmesquinmœ while Strophomena 

 comes under Orthotetinœ. 



In his recent paper «The Anticosti Island Faunas» ^) W. H. 

 Twenhofel expresses a different opinion. He proposes (p. 25) the term 

 Strophoprion «for those resupinate forms of the Strop homenidae which are 

 like Strophonella except that they have some ten or a dozen denticula- 

 tions along the hinge line instead of a completely denticulated hinge 

 margin». And further down he writes: «In one line of development 

 there are Strophomena — Strophoprion — Strophonella ; in the other Rafines- 

 quina — Leptaena? (ceres — nitens stock, not rhomboidalis) — Brachy prion — 

 Stropheodonta» . 



We have certainly here two very different opinions expressed. In 

 order to get this important question decided, it is necessary to consider the 

 different types of Strophomenids that are met with at about the time when 

 the older genera, Rafinesquina and Strophomena, disappear and the younger, 

 Stropheodonta and Strophonella appear. In other words the youngest 

 representatives of the older groups and the oldest of the younger. 

 In Hall and Clarke's «Introduction» relatively few of these forms are 

 considered, the great majority of species that are mentioned, belonging to 

 the said genera, being either Ordovicic or Devonic. This is naturally 

 explained by the fact that a large part of the Siluric is rather poor 

 in fossils in the best known regions of North America. In Anticosti the 

 lower part of the Siluric, that is of special interest here, contains a very 

 large number of fossils, including Strophomenids. 



In our material, we have in two forms only, possessing convex 

 ventral and concave dorsal valves, observed a denticulated hinge margin ; 

 some few others probably show the same feature but it has not been 

 direcdy seen. These two forms are Brachyprion semiglobosum var. 

 norvegicum and B. Walmstedti Lindstr. We have now the question : 

 Do these forms in exterior or interior characters differ so strongly from 

 older types of Strophomenids that have not the denticulated hinge (and 

 therefore are referred to Rafinesqiiina) that they cannot be considered a 



1 A classification of the Brachiopoda, American Geologist. Vol. XI, 1893. 



A Synopsis of Am. Fossil Brachiopoda. Bull. U. S. G. S. No. 87, 1897 Chapter: 

 Brachiopoda in Eas'man's English edition of Zittel's text-book of Paleontology, 1913. 



'•* Geol. Survey of Canada. Museum Bull. No. 3, 1914. 



