262 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



sixty-eight Bryozoa of oiir western area, all but five are in calcareous 

 beds here — principally in shales. The five alluded to are three spe- 

 cies of Graptolites in argillaceous sandstone, Retepora Clintoni in sili- 

 ceous sandstone, and Fenestella tenuis in the Clinton beds of iron-ore. 



The 41 Welsh Bryozoa present only ten species strictly arenico- 

 lous, eleven inhabiting pure clay, and nine carbonaceous shale ; the 

 rest are in highly calcareous beds. Of the 82 species of Zoophyta 

 of known matrix in the New York area, only five are met with in a 

 non- calcareous rock. They are Dictyolites BecJcii, Discophyllum 

 peltatum, and D. sp. indet., in argillaceous sandstone, and Catenipora 

 escharoides and Phcenopora consteUata in the Clinton iron-ore. 



The 81 "Welsh Zoophyta are more freely distributed ; but they are 

 four times more numerous in calcareous strata than out of them. 



The Crinoidea and Cystidea of New York wholly affect strata 

 containing hme, especially when shaly. In Wales, this does not 

 hold true ; but nevertheless three-fourths of these fossil appearances 

 are in calcareous strata. 



The Cystidea abound in the Lower Silurian limestones of the Ottawa 

 Eiver, about Yictoria ; but none have been hitherto found in the 

 Silurian beds of New York. Out of 323 appearances of Trilobites 

 in Wales, nearly one-half are in strata destitute of lime. It is in 

 argillaceous sandstone and in argillaceous limestone that they are 

 very frequent (48 and 49 occurrences respectively). The proportion 

 of arenicolous Trilobites in New York is as one to nine, the other 

 and far larger portion being in argillaceous limestone and argilla- 

 ceous shale, with twelve more in pure carbonate of lime — an unusual 

 circumstance. The four Crustacea in purely argillaceous and arena- 

 ceous beds are Homalonotus delphinocephalus and Olenus asaphoides 

 (both in argillaceous sandstone), Agnostus pisiformis (in the same 

 stratum, but micaceous), and Beyrichia lata (in Clinton iron-ore). 



Of 254 species of Brachiopoda in New York, of known matrix, 

 only twenty-four are found in non-calcareous sediments ; whilst in 

 Wales the distribution is much more general, there being 207 ap- 

 pearances in the beds just spoken of, against 309 in the limestone- 

 rocks. The reason of this may be that in Wales lime in small 

 quantities pervades many sets of layers which are not classed as 

 calcareous. In New York the appearances are most numerous in 

 argillaceous limestone ; in Wales, in Bala Limestone and argil- 

 laceous sandstone. Most of the genera of Brachiopoda furnish ex- 

 amples of arenicolous and argiUicolous species. They are easily found 

 on reference to the Tables. 



In the New York area aE. the 44 Monomyaria, excepting six, are 

 in highly calcareous sediments, eleven being in pure limestone. Four 

 of the six above excepted are in argillaceous sandstone. In Wales, 

 the Monomyaria appear 27 times in calcareous strata (never in pure 

 limestone), and 20 times in arenaceous beds. We know the matrices 

 of 49 Dimyaria in New York. These appear 44 times in lime-rocks 

 (most numerously in the argillaceous), and 14 times in sandstone- 

 rocks — chiefly in those of the Hudson-River group which contain 

 alumina. 



