2^2 TRANS. ST. LOUIS ACAD. SCIENCE. 



miner, who works at a depth of perhaps sixty feet in the average. 

 mostly with a simple pick, in loose materials or in softened rock, 

 then we understand equally the immense advantage of the Mis- 

 souri deposits over regular vein deposits, and the reason of the 

 wonderfully rapid development of lead-mining in this State. As 

 some of the oldest mining districts in the State are as yet far from 

 being exhausted, and as very large territories containing the same 

 rocks as those old districts have been its yet very insufficiently 

 investigated by mining, a further and larger development may be 

 confidently looked for. 



Whether, or not, other lead deposits exist below that level in 

 which the present mining operations are carried on. can only be 

 decided by practical investigation. The character of the depos- 

 its, as I have described them, does not indicate that they may 

 continue to a great depth, and in various places an entirely bar- 

 ren limestone has been struck below the ore. and has been pene- 

 trated to a depth of sixty and a hundred feet without favorable 

 results. But as it happens sometimes that barren and ore-bearing 

 rock formations alternate, this may prove to be so in Missouri, and 

 the future discovery of deeper galeniferous layers is not absolutely- 

 impossible, although there is nothing to indicate them at the pres- 

 ent time. However this may be, the production of lead ores to 

 be expected from the development of those lead-bearing strata 

 which are at present known and mined will certainly be more 

 than sufficient to supply and to satisfy the present generation, and 

 there can be no reasonable fear that we shall ever see the end of 

 lead-mining in Missouri. 



On the Terebratula MormoniL 



By Jules Marcou. 



A friend has called my attention to a memoir just out. entitled 

 "On the Carboniferous Brachiopoda of Itaituba, Rio Tapajos, Bra- 

 zil," by O. A. Derby (Bull. Cornell Univ. Science, vol. i. Xo. 2) ? 

 in which a small Terebratula is described under the name Eume- 

 tria (Hall) puuctulifera Shumard, with the following synonimia : 



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