The Canadian journal of industry, science and art . ecies known as Modiolopsis modiolaris fig. Ill, so common in our Hudson River Group, belongs in all pro-bability to this division. The genus Cyrto- donta of Billings, (with its sub-genus Vanuxe- mia), may also be referred to the Orthoeoncha of this Section. Fig. 112 represents the Cyrto- donta JSuronensis (var. siibcarinata) of the lower part of the Trenton Group. Another and more remarkable species of this genus— widely known as the Megalomus Canadensis, of Hall—occurs in great numbers in the Onondaga Salt Group, (UpperSilurian), of Canada W

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The Canadian journal of industry, science and art . ecies known as Modiolopsis modiolaris fig. Ill, so common in our Hudson River Group, belongs in all pro-bability to this division. The genus Cyrto- donta of Billings, (with its sub-genus Vanuxe- mia), may also be referred to the Orthoeoncha of this Section. Fig. 112 represents the Cyrto- donta JSuronensis (var. siibcarinata) of the lower part of the Trenton Group. Another and more remarkable species of this genus— widely known as the Megalomus Canadensis, of Hall—occurs in great numbers in the Onondaga Salt Group, (UpperSilurian), of Canada West, and more especiallyin the neighbourhood of Gait. It is foundchiefly in the form of internal casts, as shewnin the figures 113 and 113 a. The lamellibrancJis of the third group, IntBgro-PaLlialia, have the upright (or right andleft) position of the orthoeoncha of Section I.,but, unlike these latter, they possess a pair ofshort * respiratory tubes. The muscular im-pressions, two in each valve, are connected, as in the forms of the Fig. Fig. 112.

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Keywords: ., bookcentury1800, bookdecade1850, bookpublishertoron, bookyear1856