266 bulletin: museum of comparative zoology. 



Stictoporella, Rhinidictya, Phylloporina, and Clitambonites beds 

 (Black River to ^Middle Trenton) of Minnesota, was identified from 

 the Kunda of Russia. These forms are evidently of little value in 

 direct detailed correlation, since the two species found in Bu would 

 correlate that formation with the Upper Trenton, while the two found 

 in Bm correlate that formation with the Black River and Lower 

 Trenton. One of the species has a range equal to almost the whole 

 Ordovician of Russia, and another has a very long range in America, 

 so that no very valuable conclusions can be derived from them. 



In considering the Bryozoa, it must be remembered that as yet only 

 a few specimens belonging to the genus Xicholsonella, have been 

 found in the American Beekmantown,and that the fairly large bryozoan 

 fauna of the Chazy is as yet undescribed. The comparison of the range 

 of genera in America and Russia does not, therefore, mean much, for 

 many of the American genera now supposed to start in the Black River 

 will probably be found to have their beginnings in the Chazy. There 

 are, however, one or two interesting points to be noted in this connec- 

 tion. Bassler distributes the twenty-six species which he describes 

 under eighteen genera (compare with seventy-seven species of trilobites 

 in eighteen genera, and forty-five species of brachiopods in fifteen 

 genera). Of these eighteen genera, only three are not found in Amer- 

 ica (compare with eight out of eighteen in the trilobites and eight of 

 fifteen in the brachiopods). Three more are very peculiar, in that 

 their American range begins much later than in Russia. One of them 

 is known in this country from the Richmond to the Mississippian, 

 another from the Niagara to the Coal Measures, and the third is 

 wholly Devonian and Mississippian. A single one is found in the 

 American Beekmantown, and the remaining eleven are known from 

 the Stones River or Black River to the Richmond, excepting for one 

 or two which do not start till the Middle or Upper Trenton. Looking 

 over the table showing the range of the various species in Russia, we 

 find that four species are confined to Bu, one is confined to B,i and 

 B,ii, nine are found only in Bm, eight pass from B into C, but do not 

 extend further, and that three begin in B and continue into D, E, or F. 

 Thus, among the Bryozoa, there are only five species common to Bu 

 and B,ii, and of these only one does not continue into C, M'hile there 

 are eleven common to B and C, which is very unlike the condition 

 which obtains among the other classes. For instance, in the seventy- 

 seven species of trilobites, nineteen are common to Bn and Bm, and 

 only thirteen pass from B into C, and some of these cases must be 

 considered as doubtful, since they come from that district on the 



