GASTROPODA. 



'"-' 



bore and belo .-dlan ke*ls, passing apparently over the** and then acroM the concave central 



pace with a slight backward curvature (see flg. 59, pi. LXX); aperture subquadrate. very slightly pro- 

 : l.'luw ; uuiMlli-al perforation extrvm-ly uilnut.- i.r wn< 

 Tin- small carin.i ju-i lioneath th-- suture llm- .litlnnulsh.-s tin-* species from 8. prison. 



- figure (lor. cit ) isrorrrrt. then the Canadian types of the species must have a wider apical 

 h.in th- Minnesota and Wisconsin specimens above descrlbi-d. The angle of th<> Illustration in 



- about 28, while It Is not over 15 in our examples. We are, however, Inclined to d-mln. tin- 



th.- Canadian Illustration, especially since Hillings, after giving the apical an^U-of 1>I Eunema 

 at "about If" says that his specie* Is distinguished from . pagodii only )>y the absence of th- 



upper carlna. 



Formation and JoeuWfy.- Black River group, Pauquetles rapids, Ottawa river, Canada ; Phylloporlna 

 bed, near Cannon Falls, Minnesota; "Upper Buff limestone," near Ik-lull. Wisconsin. 



CWbeMcMu.-i .f Wisconsin; E. O. Ulrlch. 



Family Kl OM I'HAI.I I >.l -.. 



This important family, according to our opinion, is to be viewed as an off-shoot 

 from the same early type in which both the Raphistomida: and Plturotomariida also 

 originated. It is to be expected, therefore, that, although some of the earliest forms 

 of the family underwent very rapid and strongly marked changes, the majority are 

 decidedly like their contemporaneous cousins. For the same reason it is evident 

 that for some of the "majority" it is difficult to decide whether they had best be 

 regarded as Euomphalidce or as members of one of the other families. With our 

 present limited knowledge of their progenitors.it is perhaps impossible to arrive at 

 positive conclusions. 



Already in the Calciferous and Quebec groups, which contain the earliest fully 

 known representatives of the present subclass, we find unequivocal members of 

 the family. Of them we may mention Eccyliomphalus intortus, distans and cnnadensis 

 of Billings, E. (Caularops) lilnit\>rmis Whitfield, Straparollus quebecensis Billings, and 



nphalus calciferus Whitfield. The Eccyliomphali are clearly of the line of 

 development which found its continuance in E. angelini LindstrOm, of the Swedish 

 Lower Silurian. /.'. undulutus Hall, of the Stones River group, and our Trenton 

 species, E. subrolundus; and possibly its culmination in the Upper Silurian shells 

 from the islauil of Gothland, described by LindstrOm as Euomphalus iriqudrus and 

 neon. ing this line of development, we are fully convinced that 

 it stands in only very remote genetic relationship to the large group of Upper 

 Silurian < arKoniferous species which is typified by Euomphalus pentangulatus, the 

 derivation of the latter group from the equally ancient types of Ophiletu, being, as 

 we shall show presently, very easily demonstrated. 



The immediate progenitor of the Calciferous Eccyliomphali, we conceive to 

 have been a form like our EC. contiguus with contiguous, though perhaps narrower, 



* Wtlootf* HunMii|i>alM ilmmliiii (Memog. P. 8. (tool. flur. rot. Till. p. ifff: IMS) may rcpraMnt continuation of tbU 

 t rp. bat hU ipol U K> Imperfect Ibtt It U Inpanlbl* to rrlr at MtUfkCtory coDCluloo* rpctlo< It. 



