[.A 



i . i- 







thickened at the outer and inner corner-. Tins agrees with Ophibta, as does 

 :I!MI the form .f th> aperture, and tlie course of the lines of growth. Finally, the 

 position and character of the "collar " i- certainly much more like the notch-keel of 

 Ophilet-i than the more obtuse keel or undulation which murks the position of the 

 rather broad ami more shallow upper sinus in Eccyttompkaku. 



Loosely coiled or disconnected whorls we do not consider as an essential 

 charact. ' n.<. All the species may perhaps exhibit a proneuess to 



assume such a condition l>ut it is certainly not very apparent in any of the American 

 species. Of the latter, /.'. mhtinttts Whitfield .-p.. (see plate LXXIV) is the only one 

 known to u* having all the whorls separate, and it is doubtless closely related to the 

 KurojH'an /.'. n/atus Roemer sp., the type of the genus. Then we have l-'-.tri-inijtiltta Whit- 

 tield sp., also from the Calciferoii- at 1'iovidence island and Fort Cassin, Vermont, 

 which is exceedingly like the SwedMi /.'. ri'i>lirala Lindstromsp., especially when it has 

 the inner whorls in contact. The next species, our E. beloitensis, is from the Stones 



i jrrmip. It, like the preceding, hasa representative in Kurope, being apparently 

 very similar to /.'. hwald sp. All the whorls are in contact in this 



species excepting occasionally the apertural portion in old examples. The fourth 

 American species is the Oplnlf 'fnsis of Billings, from the Trenton of Canada, 



while the fifth ami. so far as known, the last is the Ophilrhi mrenana of Meek and 

 \\ orthen. c;ists of which are not uncommon in the Trenton group of Minnesota and 

 Illinois. In )>oth the whorls are always in contact. From the foregoing statements 

 it is e\ident that, in the development of the genus from the Calciferous on, the 



it.- or free character of the whorls became gradually less ami finally was lo-t 

 entirely. All the other characters, however, ure maintained with rare persistency. 



If Kr>-i/lii>i>tmi* ami linjittixtnma are sections of the same line of development, 

 then the evidence of their geological distribution indicates the former as the parent 

 stock and not the la mv ll'ijthitloma occurs so far as known first in the Chazy 



when />, -i/Hnfitem*. which enjoyed its greatest development in the Calciferous 

 formation, had already begun it- decline. We do not wish to deny that much may 

 he said in favor of -iich a derivation of Ituphistonin, still we are confident that the 

 modifications required are more difficult to prove and altogether less rational than 

 in the view which derives the genus from /'//)/(/'.>////';./. l!illinu r - ha- de-cribed a 



number of low-spired <'alcif t >rous ;l nd (jup.bec -| j,., amoii^ which we expect to 



find links connect MIL' tin- l.i-t ^emis with the t'lia/.y /,';/<// /.-/m./. His \'lr\u 

 hoiienxin and PI. Art;-/"/-/ promise the required conditi- 



In H'tfihutoma the spire of the upper - .e- from flat to gently convex, but 



so far as we have observe 1. it is never sunken; the keel form- the periphery and i- 

 di reeled outward instead of upward: the umbilicus is always smaller, and the section 



