160 LATOUCHE: GEOLOGY OF NORTHERN SHAX STATES. 



A study of these tables shows that, in the present state of our 



knowledge, the fauna of the Namhsims must 

 Homotaxial relations be taken ag a whol and that it is not 

 ot the fauna. ' . 



possible as yet to subdivide the formation on 

 paleeontological grounds alone into zones corresponding with those 

 in other countries. Among the 15 species that have been collected 

 from the lower Namhsims 6, or their nearest allies, are found in 

 the Wenlock beds of England, or their equivalents elsewhere, and 

 9 range as high as the Ludlow ; while, in the upper Namhsims, 

 among 23 species, 21 are found in the Wenlock, and only 18, 

 including 13 which also occur at lower horizons, are Ludlow forms. 

 Other anomalies may be noticed ; for instance, Pentamerus 

 cf. oblongus* and a Lindstrcemia, closely allied to, if not identical 

 with, L. (Peiraia) subduplicata, both characteristic Llandovery 

 forms in England, — though in America the former is found at a 

 higher horizon, — -are found here in the upper beds ; and on the other 

 hand Orthonota, which is a typically upper Ludlow shell, occurs 

 low down in the lower division. At the same time we have 

 genera and species like Mimulus, Phacops longicaudatus, Orthis 

 rustica, 0. biloba, Conchidium biloculare, Spirifer sulcatus, and 

 Nucleospira piswn, which are characteristically Wenlock, and it is 

 evident from a glance at the table that an overwhelming majority 

 of the species occur in this formation, either in England or in 

 its equivalents elsewhere. The formation then, taken as a whole, 

 may be considered to be homotaxial with the middle Silurian or 

 Wenlock beds, but with an admixture of species from higher and 

 lower horizons. In order to account for the presence of these we 

 require to know more about the geology of intervening regions. 

 It may be remarked, however, that only 10 species occur also in 

 Bohemia and 6 of these are wide-ranging forms like Calymene 

 Blumenbachi, Leptcena rhomboidalis, Orthis elegantula, Pentamerus 

 galeatus, Atrypa reticularis, and Spirifer sulcatus. As Mr. Cowper Reed 

 remarks : — 



" We observe the presence of many species of brachiopods allied to or 

 identical with those found in beds of Wenlock age in Northern and Western 

 Europe, in fact there seem to be very few peculiar or local species. The 

 only discordant element is Mimulus, which is a Bohemian and American 

 gonus." (Lower Pal. Fossils, N. Shan States, p. 152.) 



