BELEMNITES OF THE LIAS. 



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On Belemnites allied to Belemnites tripartitus of Schlotheim. 



Under the name " Belemnites tripartitus " foreign palaeontologists have assembled a 

 considerable variety of forms, some distinction among them being made after the manner of 

 Quenstedt, who, in his ' Cephalopoda,' employs as general terms such titles as tripartitus, 

 paxillostis, cowpressiis, brevis, digitalis ; and qualifies them by addition of other terms, as in 

 B. tripartitus snlcosus, or by joining together even general terms, as digitalis tripartitus, 

 tripartitus paxillosus, and the like. By this mode of proceeding the idea of real specific 

 diversity is obscured, and that of a vague mixture of characters is introduced. Yet it has 

 some considerable advantages for a serious inductive study of a large Beleranitic series, 

 and will be referred to again. Others, as D'Orbigny, plainly join into one specific group 

 a large number of " tripartite" forms which seem, at first view, to claim separation. Thus, 

 under B. elongatiis this author enumerates B. admcatus. Miller, B. trisulcatus, 

 Hartmann, B. oxyconus, Hehl, B. incurvatus, Zieten, and B. propinquiis, Miinster. 

 And in his plate viii, figs. 6 — 11, the species is called B. tripartitus, Schl., though that 

 name is omitted in the text ('Terr. Jurass.,' p. 90), Voltz gives as a different species 

 B. trifidus {' Obs. sur les Belem.,' pi. vii, fig. 3) ; and Blainville had already suggested for 

 separation his B. trisidcatus ('Mem. sur les Belem.,* pi. v, fig. 13). 



On the Liassic coast of Dorsetshire these forms are so rare that I can hardly quote 

 one from personal research. One is referred to by Quenstedt as from Lyme Regis, with 

 distinct ventral groove, under the title of B. digitalis tripartitus^ and figm-ed pi. xxvi, 

 fig. 31, of his ' Cephalopoda.' He remarks that it is exactly like German (^. e. Wur- 

 temberg) examples. The Yorkshire coast produces a greater number and a greater 

 variety of such forms. 



There appear to be two principal sections of them, which in mature age may be thus 

 separated : 



Elongate, straight, three-grooved, often striated, as B. tripartitus and B. subtenuis of 

 these pages. 



Shorter, somewhat recurved at the apex, with three rather short grooves, and few or 

 no striae, as B. subadiincatus and B. vulgaris, to be noticed hereafter. 



In Mr. Simpson's work on the Lias of Y^orkshire the "tripartite" forms are employed to 

 constitute a larger number of species than appear to me necessary ; but though I have 

 had the opportunity of inspecting the fine collection at Whitby, which is the basis of 

 his work, I do not find in it a sufficient series of forms, from youth to age, of the sup- 

 posed species, to give more than a few indications of the synonymy which may guide 

 further research. 



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