Vol. 55.] ECTOilAElA AND HORMOTOMA. 259 



Foss. Cambridge Museum/ records eight species of Rormotoma, 

 namely, M. articulata, Sow., M. angustata, Hall, M.cingulata, His,, 

 M. torquata^ M'Coy, aad four forms which he does not name. 

 Of these M. articulata and M. cingulata are the only species 

 which can be placed in this genus. The specimen referred to as 

 M. angustata is a very poor cast, which, if one may judge by the 

 available evidence, appears to have more affinity with the genus 

 Eetomaria. In M. torqu/tta the lines of growth are not so oblique, 

 and it bears the characters of the true Marchisonke, so far as can be 

 discerned. It occurs merely as external moulds, and the wax 

 impressions taken from them do not show the band very distinctly. 

 The others, given on pp. 97 & 155 {op. cit.\ are merely casts, only 

 one of which exhibits the lines of growth on a portion of the surface, 

 and these prove it to have more in common with Loxonema than 

 with Bormotoma, as the tongue-shaped sinus is absent. 



Besides the two individuals mentioned above, there are eight 

 British Cambrian, Ordovician, and Silurian species known to us at 

 present, namely, JI, Salteri, Ulr. & Sco., H. (1 ) gracillima, Salt,, 

 H. (?) dubia, sp. nov., H. (? ) Piperi, sp. nov., H. Griffithi, sp. nov., 

 H. shnilis, sp. nov., H. aoitiqua, sp. nov., and U. Grayiana^ sp. nov., 

 making a total of ten. Three, however, are too imperfectly preserved 

 to admit of absolute certainty as to the correctness of their reference 

 to this genus. 



On the Continent species have been recorded from France, 

 Scandinavia, and Russia. In the first-named country D. & P. ffihlert^ 

 have described two species from the Devonian of Mayenne, namely, 

 H. Lehescontei, (Ehl., and H. davicula, CEhl., and thej^ were so good 

 as to send me the former to examine. It differs from the type of 

 Hormotoma in having more regularly convex whorls, which are less 

 closely coiled and have deeper sutures ; the lines of growth do not 

 retreat and advance so strongly, and there are traces of a spiral 

 thread in the middle of the band. The other species also has very 

 convex whorls which are detached one from the other, and according 

 to the figure the lines of growth are much the same as in H. 

 Lehescontei. The foregoing considerations show that these species 

 can hardly be regarded as members of the genus Hormotoma. 



The latest work on the Scandinaviun Silurian gasteropoda is that 

 of Lindstrom,^ in which (pp. 126-127) he divides the Murchisonice 

 into two groups, namely, Simplices and Ornat<x. The former group 

 contains four species which belong to this genus ; they are M. cingu- 

 lata, His., M.cava, Lind., M. moniliformis, Lind., Siud M. subp)licata , 

 Lind., which all agree in having smooth beaded whorls, with slightly 

 margined band and very oblique lines of growth. The other species 

 associated with them by Lindstrom are M. ohtusangulata, Lind., 

 M. comqiressa, Lind., M. attenuata, His., and M. ijaradoxa, Lind. 

 TJlrich & Scotield include the first-named in Hormotoma, but the 



^ 'Descr. qq. Esp, devon. de la Mayenne,' Bull. Soc. Etudes sci. Angers, 

 1887, pp. 18-19 & pi. vii, figs. 3-3^ & 7-7c. 



- ' Silur. Gastrop. & Pterop. of Gotland,' Kongl. Svensk, Vet,-Akad, Handl. 

 vol. xix(1884)no. 6. 



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