618 



MISS JANE DONALD ON CAEBONIFEEOUS 



Turritella}, some of the earlier palaeontologists referred them to that 

 genus. But in 1841*, A. d'Archiac andE. de Yerneuil classed them 

 together in a new genus called Murcliisonia, the possession of the 

 sinus in the outer lip being considered to distinguish them from the 

 genus Turritella and from other genera of elongated shells to which 

 they had been referred. In 1859, J. W. Salter (Geol. Surv. 

 Canada, dec. i. p. 18) separated from the typical Murchisonice 

 elongated shells composed of rounded, bead-like whorls, and whose 

 mouth is round, instead of being ovate and slightly channelled. To 

 this group he gave the name of Hormotoma, and took M. gracilis, 

 Hall, as the type. 



Whitfield (Bull. Amer. Mus. Nat. Hist. vol. i. no. 8, 1886, p. 311) 

 considers it advisable to form a distinct genus for some other shells 

 which have hitherto been classed as Murcliisonia. He calls this 

 new genus Lophospira, and defines it thus : — " Shells univalve, with 

 elongated spires, and strongly carinated or keeled volutions ; whorls 

 closely coiled in the upper part, but often becoming disconnected 

 below from a too rapid descent of the coil. Central keel marking 

 the position of a sinus or notch in the outer lip of the aperture. 

 Axis usually minutely perforate when the whorls are not discon- 

 nected. Types M. bicincta = M. Milleri, Hall, and M. lielicteres, 

 Salter." 



The exact value of these subdivisions can hardly be determined 

 at present, but possibly the discovery of better-preserved specimens, 

 and the detailed examination of the whole series of the Palaeozoic 

 forms possessing a slit in the outer lip, may eventually lead to the 

 establishment of several well-defined subgenera. 



It is a question, however, whether the Murcliisonia} may not be 

 more nearly allied to some species of Turritella than was thought 

 at one time ; for recent investigations have brought to our knowledge 

 the fact of some species of Turritella possessing a sinus in the outer 

 lip. In January 1881, Mr. Marrat, of Liverpool, first pointed this 

 out to me, and showed me some shells in the Liverpool Museum 

 with a deep, narrow slit in the outer lip, similar to that of Mur- 

 cliisonia. These shells were collected in Bass's Straits, by Capt. W. 

 H. Cawne- Warren (ship ' Bedfordshire '), Associate of the Lit. and 

 Phil. Soc. of Liverpool, who presented them to the Museum ; and 

 Mr. Moore, the Curator, kindly enabled me to obtain two specimens 

 in exchange for some fossil Gasteropoda. Mr. Marrat named this 

 species T.fissurata (in lit.). In the Journ. Linn. Soc. Zoology, vol. 

 xv. pp. 217-230, 1881, the Rev. Boog Watson described, some 

 species of Turritella with a sinus in the outer lip, obtained in the 

 dredgings of H.M.S. ' Challenger.' These have since been more fully 

 described and figured by him in ' The Yoyage of H.M.S. Challenger, 

 Report on the Gasteropoda, Zoology,' vol. xv. 1886, p. 466. The 

 depth of the sinus in Turritella seems to vary from a mere curve to 

 a deep, Y-shaped slit, as in the Liverpool shell, and also in T. 

 runcinata, Watson, and T. accisa, Watson. This sinus is indicated 



* Bulletin de la Soc. Geol. de France, t. xii. p. 154. 



