42 PROCEEDINGS OF THE ACADEMY OF 



ally in the condition of a carbonate), while more or less arenaceous and ar- 

 gillaceous matters also enter into their composition. Some of the concre- 

 tions seem to contain no organic remains, but often in breaking open others, a 

 fossil is found to have formed the nucleus around which the concretionary 

 action took place. 



It is an interesting fact that we find here, near the base of the Illinois Coal 

 Measures, a species of the remarkable genus Bellinurus, an intermediate link, 

 (hitherto only known to occur in the lower Coal Measures of England and Ire. 

 land,) between the older Trilobites, and the existing genus Limulus. In Eng- 

 land it is found enveloped in similar iron-stone nodules, at Cole-Brook-Dale, 

 where three species have been discovered, one of which [B. bcllulus, Koenig, 

 = B. rotundatus, Prestwich) is closely related to our Illinois species. 



We likewise find at the Morris locality a species of the genus Anthrapalse- 

 mon, Salter, (or a closely allied type) which in Scotland also occurs in the 

 lower Coal Measures, while neither of these genera are known in the subcar- 

 boniferous, or any lower formation. These facts furnish additional evi- 

 dences, if any were necessary, (coinciding with all the other palaeontological, 

 as well as stratigraphical, evidence) of the fallacy of an opinion recently ex- 

 pressed by a writer in the Bulletin of the Geological Society of France, that 

 our western Coal Measures, and particularly those of Illinois and the adjoin- 

 ing States, belong not to the horizon of the true Coal Measures of Europe, 

 but to the subcarboniferous or mouhtain limestone series. 



In a paper by one of the writers, published in the March number of the 

 American Journal of Science, 1865, after speaking of the general distribu- 

 tion of marine remains in our western Coal Measures, he remarked (which 

 was strictly in accordance with his observations up to that time) that after 

 more than twenty years familiarity with the fossils of the coal formation of 

 the Western States, he had never seen amongst them any terrestrial or fresh- 

 water types, other than plants. Since investigating the fossils described in 

 this paper, however, amongst which it will be seen there is believed to be a 

 Caterpillar, we can but regard the Morris bed as an exception to this general 

 rule. If the fossil to which we allude is a true Caterpillar, its presence there, 

 along with the insect described by Prof. Dana, would indicate that this bed 

 was probably deposited in an estuary, into which this little worm- like larva, 

 and the other insect, were doubtless carried from the land by an inflowing 

 stream or the ebbing tide. This suggestion also receives some support from 

 the affinities of the associated Crustacea, since the genus Bellinurus, from its 

 relations to the existing genus Limulus, might have been capable of living at 

 least in brackish waters, although the English species are associated with 

 marine forms. The genus Anthrupalsemon is also supposed, by Prof. Dana, to 

 have been related to JEglea, a fresh-water type. In addition to these facts, no 

 unquestionable, strictly marine forms of any kind have, so far as we know, 

 been yet found in this bed. 



The existence of this exceptional case (if it is such) of terrestrialand fresh 

 or brackish-water fossils in our western Coal Measures, has no bearing, how- 

 ever, against the general conclusions in connection with which the statement 

 above alluded to was made ; nor even, indeed, against the general accuracy 

 of the statement itself, since the fact of the almost exclusive and general 

 distribution of marine animal remains in our western Coal Measures, stands 

 unshaken. 



The fossils here noticed will be fully illustrated and described, and such 

 additional facts given as we'may in the mean time learn from other speci- 

 mens, in the forthcoming report of the Illinois Geological Survey, for the 

 publication of which we are happy to announce the Legislature has made a 

 liberal appropriation. 



We are indebted to Prof. Dana for the use of several specimens of some 

 of the Crustacea described in this paper, as well as for suggestions in regard 

 to their affinities; also to Dr. Stimpson for suggestions respecting the same. 



[Mar. 



