Vol. 51.] MURCHISONIA AND ITS ALLIES. 211 



several specimens. D. and P. (Ehlert 1 propose that the name 

 Marchisonia should be restricted to tuberculated shells, and suggest 

 the name Goniostropha for those which are not tuberculated, but 

 which in other points agree with the type, namely, in the possession 

 of angular whorls with the sinual band situated on the augle, and 

 generally limited by two prominent keels. But this division would 

 hardly be advisable, since some varieties of a single species (as of the 

 type for instance) would be included in Murchisonia, and others in 

 Goniostropha. D. and P. (Ehlert give M . Bachelieri, (Ehl., as the type 

 of Goniostropha, a shell which greatly resembles the smooth variety 

 of M. turbinata, with which, indeed, Mr. Whidborne 2 considers it 

 identical. It would be well, however, to limit the name Murchisonia 

 to shells having more or less angular whorls with the sinual band 

 situated on the angle or widest part of the whorl, excavated and 

 bounded by keels, or else formed of a single prominent keel ; the 

 mouth oblong and slightly channelled below ; generally ornamented, 

 the ornamentation consisting of tubercles, plications, or keels. If 

 this be done, some sections or subgenera must be accepted for the 

 forms which differ from this as type. 



The name Hormotoma was given by Salter 3 to shells distinguished 

 from the typical Murchisonia} by having smooth, rounded, bead-like 

 whorls, with a flat sinual band and a circular mouth. The Silurian 

 M. gracilis, Hall, is the type. D. and P. (Ehlert retain this section, 

 and suggest the name Ca?lucaulus i for somewhat similar forms which 

 likewise have smooth whorls with a level sinual band, but differ in 

 having the whorls more flattened, the sutures shallower, a narrow 

 but very deep umbilicus, the columella completely vertical, and the 

 peristome reflected. M. Daviclsoni, (Ehl., is given as the type. In 

 addition to these, I have suggested the names .Hypergonia, ° Stego- 

 ccelia, 6 and Oerithioides for other sections. The first is characterized 

 by the sinual band being placed above the angle, in other points it 

 resembles the type of the genus. M. quadricarinata, M'Goy, is the 

 type of this section. Stegocoelia also has the band above the angle, 

 and the umbilicus frequently open when young, but closed by a 

 reflection of the inner lip in the adult. The examination of a larger 

 scries of examples has led me to the conclusion that the umbilicus 

 is not always open in youth, but the inner lip is invariably widely 

 reflected on the columella in the mature state. This feature, together 

 with a shorter spire, distinguishes it from the typical Hypergoniai. 

 21. compacta, Don., is the type. 



I proposed retaining for a section the name Oerithioides, originally 



1 Bull. Soc. d'Etudes Scientifiques d' Angers, 1887, p. 13. 



2 'Monogr. Devon. Fauna of the South of England,' p. 308. 



:1 Geol. Surv. Canada, ' Pig. & Descr. Canad. Organic Remains,' dec. i. (1859) 

 p. 18. 



' Op. supra cit. p. 20. 



' ' Note9 on some New and Little-known Sp. of Carb. MurcJiisonia,' Quart. 

 Jotirn. Geol. Soc. vol. xlviii. (1892) p. 564. 



" • Descr. of some New Sp. of Carb. Gasteropoda,' Quart. Journ. Geol. Soc. 

 vol. xlv. (1889) p. 623. 



