■WH1TEAVE8.] LARAMIE AND CRETACEOUS INVERTEBRATA. 47 



Anisomton alvectlus, Meek & Hayden. 



Heldon alveolus, Meek and Hayden. 1856. Proc. Ac. Nat. Sc. Phil., vol. VIII., 



p. 68. 

 Anisomyon alveolus, Meek and Hayden. 1860- Am. .Tour. So. & Arts, \ol. 



XXVIII., (2nd series), p. 35. 

 -An-isomyon alveolus, Meek. ls7(i. Kep. U.S. <3eol. Surv. Terr., vol. IX., p. 292, pL 



18, figs. 4, a, b. 



White Mud Eiver (or Frenchman's Creek), near the 49th Paralle 

 :and south of "Woody Mouotain, G. M. Dawson, 1874, H. M. JSTort 

 American Boundaiy Commission: one imperfect specimen. 



Anisomyon centrale, Meek. 

 Plate 7, flgs. 1, 1 a, and 2, 2 a. 



Anhomyon ontntle, Meek. 1S72. Eep. U- S. Geol. Surv. Terr. for 1870, p. 312. 



White. 187G. U. S. Expl. & Surv. W. of 100th Merid., p. 194, 

 pi. 18, fig. 8. 

 " " White. 1877. Hayden's U. S. Geol. & Geogr. Surv. Terr. 



Idaho and Wyoming, p. 303, pi. 9, figs, la, b, c & d. 



Old Wives Creek, Township 10, Eange 11, west of 3rd Principal 

 Meridian, E. G. McConnell, 1884 ; four large and well preserved casts 

 ■of the interior of the shell. 



No two of these sjoecimens are alike either in shape or in surface 

 markings, although they all agree to a certain extent in their conical 

 form, elevated apex and in their being marked with from four- to six 

 radiating furrows. In two of these casts the apex is nearly central, 

 but in the other two it is placed very near to the anterior end, and 

 these latter approach rather nearly to the A. horealis, Morton (sp.), 

 •especially to the specimen figured under that name by Prof. Whitfield 

 ■on plate 12, fig. 23 of the " Palajontology of the Black Hills of Dakota.'' 

 Moreover, in each of the specimens collected by Mr. McConnell, the 

 radiating furrows differ both in number and in their relative position. 

 In one of the casts, too, there is a distinct and rather prominent ridge, 

 which extends from the beaks backward to the posterior end of the 

 liase, and this is quite wanting in the other three. 



In reference to Colorado specimens of A. centrale, Dr. C . A. White 

 makes the following remarks, which are quite as applicable to those 

 from Old Wives Creek. " This species seems to be at least as distinct 

 from any of other published forms as they are from each other, but 

 cspecific variation in this genus is evidently very great. Indeed, I 



