1014 THE PALEONTOLOGY OF MINNESOTA. 



LHormotoma gracllls. 



they have or have not been derived from elongated species of Lophospira like L. 

 bowdeni Safford. 



Besides the five Trenton and Cincinnati species about to be described, we refer 

 here Murchisonia anna, M. simulatrix and M. vesta, three species described by Billings 

 as occurring in the Calciferous in Canada; M. gracilens Whitfield from the same 

 horizon in Vermont; M. procris Billings, from the Black River group of Canada; 

 M. moniliformis, M. obtusangula and M. subplicata, Gothland species described by 

 Lindstrom; and M. hebe Billings, Gaspe of Canada. M. cingulata Hisinger (as figured 

 by Lindstrom) and M. egregia Billings, have the band too low to be counted as typical 

 members of the genus, yet, it is probably best to place them here. We have already 

 mentioned M. attenuata Hisinger, and M. artemesia Billings. M. aailis Billings, 

 Quebec group, Canada, as is the case with other species described as Murchisonia, 

 may belong here but is not sufficiently known to permit us to say that it does. M . 

 teretiformis, of the same author, provided the Manitoba specimens identified by 

 Whiteaves with this species are really the same as Billings' original types, has all 

 the characters of Hormotoma, despite the great size which this shell attains.* 

 (Ehlert describes two species from the Devonian of France as M. (Hormotoma) 

 lebescontei and M. (H.) clavicula. The same author proposes Goniostropha as a section 

 of Murchisonia and includes in it several of the species that we refer to Hormotoma. 

 If Goniostropha is to be recognized it must be for the reason given on page 1012. If 

 these are not sufficient then the American species M. desiderata, M. maia and M. leda 

 of Hall, together with some of the European shells which (Ehlert places in his 

 proposed section, must be regarded as congeneric with the Silurian species of 

 Hormotoma. As defined by (Ehlert, Goniostropha is clearly an incongruous 

 assemblage. 



HORMOTOMA GRACILIS Hall, and varieties. 



PLATE LXX, FIGS. 18-3 and ?42-43. 



Murchisonia gracilis HALL, 1847, Pal. New York, vol. i, p. 181 (not SALTKK, 1859, Can. Org. Rem., Dec 



1, p. 22.) 



Murchisonia angustata HALL, 1847, Pal. New York, vol. 1, p. 41.* 

 Comp. Murchisonia gracilens WIIITKIELD, 1889, Bull. Amer. Mus. Nat. Hist., vol. 11, p. 53, pi. vin, 



fig. 14. 



* We are strongly Inclined to doubt that the Manitoba specimens, which are from the Trenton limestone (Fusispira or 

 Maclurea bed), are specifically the same us the Hudson River group, Antlcostl, originals of M. teretiformti. The apical 

 angle In the former Is 35" or more, while Billings gives the angle for the Antlcostl types at 27. Since the foregoing was 

 placed In the printer's hands, Mr. .!.!'. Whiteaves has kindly sent us the two best specimens of these Manitoba anil Antlcostl 

 forms in the museum of the Canadian survey. As a result of our comparison, we are now firmly convinced that the two 

 forms are specifically distinct, differing from each other In the same manner as //. IjttticlncUi and H. trentonennte. The 

 Manitoba species resembles the former, having more whorls, especially In the upper half of the spire, than the true //. 

 ttretiformit . 



t As will be noticed, the description of M. anguslata occurs on an earlier page In the work cited than that of M, yractfis, 

 and If we followed the usual custom In such cases the first name would have been adopted for the species Instead of the 

 econd. But as the date and authority for thetwo names Is the same, and as the name anfjustata has been scarcely recog. 

 nlzed while .H. gmcUff has been described and quoted perhaps hundreds of times since 1847, It Is evident that the latter has 

 the better right to be letalned for the species. 



