304 bulletin: museum of comparative zoology. 



the upper part is a gray marly limestone which in places is full of 

 corals. Either division is readily distinguishable from the Wesen- 

 berg (Schmidt states that the Lower Lyckholm resembles the Wesen- 

 berg), for the latter is far more hard, more compact, and finer grained 

 and partakes more of the aspect of a lithographic stone. I dissent 

 from the general statement of Schmidt that few corals occur in the 

 Lower Lyckholm. Locally they are not uncommon, but there are 

 not nearly so many as in the Upper Lyckholm and the Borkholm. 



Bassler apparently was misled by the labels accompanying his 

 specimens in considering that the Lower Lyckholm is characterized 

 by Maclurea and Subulites and in respect to the gastropods, he 

 appears to have reversed the sequence. Maclurea may occur in the 

 Lower Lyckholm; but I have not seen it there, while it is common 

 in the Upper Lyckholm. Subulites and large Hormotomas range 

 throughout, but the latter are more abundant in the upper beds. In 

 seeking for equivalents in American deposits, it is my judgment that 

 no correlative value can be placed on these large gastropods of general 

 jSIiddle Ordovician aspect. Bassler now agrees in this view, for since 

 his correlation of the supposed Lower Lyckholm he has learned of 

 numerous examples of the reappearance of faunas, and of the close 

 resemblance of the North American Black River and early Trenton 

 faunas to those of the Richmond. 



Although Bassler placed considerable emphasis on the Bryozoa 

 in drawing his deductions relating to a time break, he appears to have 

 relied more on the general aspect of the fauna. In respect to the 

 Bryozoa it would be well to review those forms which he had in mind 

 as indicative of Middle Ordovician time; these are Corynotrypa bar- 

 heri, Diplotrypa petropolitana, Dittopora colliculata, StcUipora constel- 

 lata, and Stomotopora araclinoidca. Each of these species is said to 

 occur at Hohenholm, of which the present exposures are quite cer- 

 tainly the Lower Lyckholm and such was probably true of the older 

 ones as the topography does not lend itself to the view that strata 

 much higher than those now shown were formerly exposed. Ditto- 

 pora colliculata and Diplotrypa petropolitana also occur at Pallokiill 

 and the latter at Paope; but as they occur at these latter localities 

 with at least thirteen other species of the Lyckholm Bryozoa, consid- 

 ered as evidence of " Silurian affinitv," it follows that thev must 

 almost wholly be neglected as evidence of age. Diplotrypa petro- 

 politana, moreover, is so long ranging that it has hardly any strati- 

 graphic value. Corynotrypa barberi and Stomotopora arachnoidca 

 occur at Hohenholm growing on Richmondian and Silurian corals 



